PHOTONIC IS A NEW DRIVER OF GALLIUM ARSENIDE MARKET
It is shown that placing a diffraction microstructure on the flat surface of one of the refractive lenses of a high-aperture triplet can simultaneously satisfy the correction conditions for both chromatic and monochromatic aberrations and obtain lenses designed for the middle and double infrared ranges having sufficiently high optical characteristics.
N. A. Kulchitsky 1, A. V. Naumov 2, V. V. Startsev 2
State Research Center of the Russian Federation, Joint-Stock Company “Scientific-Production Association “Orion”, Moscow, Russia
Joint-Stock Company “Optical Mechanical Design Bureau “Astron”, Lytkarino, Moscow region, Russia
The article presents the results of a brief analysis of the GaAs wafers market, provides an overview of the main products of optoelectronics, lists the world leading manufacturers of GaAs products (ingots, wafers and epitaxial layers) and considers the situation of the Russian base for the production of GaAs materials. The double semiconductor gallium arsenide (GaAs) compound is a traditional microwave electronics material. Until recently, one of the fastest growing market segments for the use of this material was GaAs high-frequency integrated circuits (ICs) for mobile telephony. However, the paradigm for the development of the GaAs market is changing. Photonics is becoming a new engine for the development of the global gallium arsenide market.
Keywords: gallium arsenide, LEDs, laser diodes, VCSEL, EEL, radars
ARSENID GALLIUM (GaAs):
HISTORY AND PROSPECTS
GaAs production appeared and developed as the introduction of technologies for creating microwave electronics material. In the mid 60s of the last century, studies of the properties of GaAs began simultaneously in the USA and the USSR. They culminated in the development of high-speed integrated circuits (ICs) used in “smart” fire control systems and in supercomputers. The industrial development of the processing of GaAs wafers with a diameter of 150 mm led to a significant reduction in the cost of microwave transistors. This ensured their widespread distribution in all sectors of application: from mobile phones and base stations to radars and millimeter-wave communication systems [1–2]. GaAs is also widely used in optoelectronics – light-emitting diodes (LEDs) are made on the basis of gallium arsenide. The invention of the first LEDs emitting monochromatic light when connected to a current source relates to the 1960s. Since then, microwave applications and LED applications have divided the GaAs market. However, it seems that the GaAs development vector is finally changing: from microwave electronics to photonics. The year 2017 can be considered a milestone – the moment the appearance of the 3D face scanning function in iPhone X smartphones using GaAs laser diodes with a vertical emitting resonator (VCSEL) (Fig. 1). The main types of devices based on GaAs are given in Table 1 .
METHODS FOR PRODUCING
GaAs SINGLE CRYSTALS
Industrial GaAs single crystals can be divided into 2 large groups:
Semi-insulating (SI) GaAs with high resistivity / intrinsic conductivity (107 Ohm • cm). It is used in the manufacture of high-frequency ICs and discrete microelectronic devices. In addition to high resistivity, SI GaAs single crystals must have high carrier mobility and high macro- and microscopic uniformity of the distribution of properties both in the cross section and along the length of the grown ingots.
Doped (SC) GaAs n-type conductivity with a low dislocation density. Single crystals of heavily doped (1017–1018 cm–3) GaAs, in addition to high conductivity, should have a fairly perfect crystalline structure. They are used in optoelectronics for the manufacture of injection lasers, light and photodiodes, photocathodes, and are material for microwave oscillators. Chromium-doped gallium arsenide single crystals are used in IR optics.
Three methods of growing are used in the industrial production of GaAs single crystals: the Czochralski method with liquid encapsulation of the melt with a layer of boric anhydride (Liquid Encapsulated Czochralski – LEC), the Bridgman method of horizontal directional crystallization (Horizontal Bridgman – HB) or “crystallization in a moving temperature gradient” (Horizontal Gradient Freeze – HGF) and the method of vertical directional crystallization (VDC) also in two versions (Vertical Bridgman – VB and Vertical Gradient Freeze – VGF).
The most important feature of the LEC method (Fig. 2a) is that the single crystal is grown at sufficiently large axial and radial temperature gradients near the crystallization front, i. e. in the field of maximum plasticity of the material. A consequence of crystal growth at high temperature gradients in LEC technology is a high dislocation density. Typical ND values in undoped single crystals are up to (1–2) ∙ 105 cm–2 at an ingot diameter of 100–200 mm. The LEC material has a more uniform distribution of resistivity across the plate area.
The material obtained by the VDC method (Fig. 2b) has a lower dislocation density. The main quality requirements for doped semiconductor (SC) gallium arsenide as a substrate material are low resistivity. This is achieved by introducing an impurity of silicon (n-type) or zinc (p-type) in the required concentration and high structural perfection. The latter quality is due to the fact that in the process of epitaxy, dislocations from the substrate are inherited into the epitaxial layer, which is an active element of the future light-emitting device. Unlike microwave devices, in devices that generate radiation, the presence of dislocations in the active regions of light-emitting structures is undesirable, since it leads to rapid degradation of the characteristics of the device. Accordingly, the requirement of a low dislocation density (ND) is a basic requirement for a heavily doped material used as a substrate for light-emitting structures. In practice, the following gradation has developed: in the production of LEDs, crystals with a dislocation density ND <5.103–1.104 cm–2 are used, and in the manufacture of lasers with ND < 5.102 cm–2.
A cost feature of the production of optoelectronic devices in comparison with the production of microwave ICs is the difference in the contribution of manufacturing operations to the cost of products, that the predominant part of the cost of the device is accounted for by operations performed after the structure is divided into separate chips. Accordingly, in the production of optoelectronic devices, increasing the area of plates is not so relevant. Therefore, in the global production of LEDs and lasers, plates with a diameter of up to 100 mm are still used in large volumes. And this is happening everywhere, despite the fact that industry has mastered the production of single crystals with a low dislocation density of a larger diameter of 200 mm.
Using two methods, the LEC method and the VDC method, both SC GaAs and SI GaAs crystals can be grown. It is important to emphasize that single crystals grown by the WNC method have a higher prime cost than those grown by the LEC method. This is due to a lower crystallization rate (4–5 times) and the exclusion of re-seeding operations from the technological cycle. Comparing the set of characteristics inherent in the devices obtained by different methods of cultivation, you can see the difference. For most microwave applications, it is preferable (at least economically) to use LEC-GaAs, while for the manufacture of LEDs, as well as for all optoelectronic applications, it is preferable to use GaAs obtained by the VDC method. These technical solutions, obtained thanks to great practical experience, are uncontested (Table 1). Therefore, both methods are present on the market, but with a significant predominance of VDC. If in 2011, LEC-GaAs crystals dominated the market, in 2016 the material obtained by the VGF method was 62.93%, while the LEC material was only 26.97%. Later, according to analysts, this trend will continue (Fig. 3)
GaAs OPTOELECTRONIC APPLICATIONS
The appearance of blue (in the mid 1990s) and white LEDs (at the beginning of the 21st century) and a constant decrease in cost made it possible to expand the use of LEDs as indicators of the operation modes of electronic devices to illuminate liquid crystal screens of various devices. Subsequently, the use of LED primary colors (red, blue and green) made it possible to design displays from them with the output of full-color graphics and animation. The service life of LEDs, which is 6–8 times longer than the longevity of fluorescent lamps, the relative simplicity of working with them at the stage of assembly of products, and the absence of the need for regular maintenance, have all made the light sources the leaders at the stage of competition with more traditional sources: gas-discharge and luminescent lamps, as well as incandescent lamps.
LED consists of epitaxial layers of GaAsP or InGaAsP grown on a GaAs substrate. The range of their radiation extends from pale green to red light. AlGaAs LEDs on GaAs substrates emit red to IR light. In the early 2000s, the SD industry entered a new stage of development. This was due to the fact that the bright and super-bright LEDs were chosen when they were used as sources of new generation general lighting systems, where they replace traditional incandescent and fluorescent lamps. Recently, new devices have appeared – micro-LEDs. They combine the advantages of high efficiency, brightness and reliability with a shorter response time, which allows you to create lighter, thinner and more flexible displays with the advantages of energy saving. Such devices are popular in applications such as wearable devices, cars, large televisions, augmented reality (AR), and more.
GaAs-based devices are produced by gas phase epitaxy of organometallic compounds (MOCVD), high temperature gas epitaxy (HT CVD), or molecular beam epitaxy (MBE) on a GaAs substrate. In total, epitaxial reactors with a total value of more than 1 billion US dollars are operating in the world today. To ensure their operation, more than 100 tons of gallium and arsenic per year are used in the form of high purity compounds. By 2025, it is expected that the number of reactors will increase by more than 6 times (Fig. 4), mainly under the influence of the growth of laser LEDs and micro-LED applications [5, 6].
Laser diodes (VСSEL, EEL, etc.)
Apple’s iPhone X smartphone was the first consumer device to use face recognition technology – IR-SD scans the user’s face and builds a 3D model. In iPhone X, 150 mm GaAs substrates are used to fabricate VCSELs and photo detectors used in face recognition. Given the potential adoption of this technology by all Android platforms, analysts expect this segment of the GaAs wafer market for VCSEL to grow 58% annually until 2023, and the VCSEL market will grow to 3,775 million USD in 2024. It should be remembered that only two years ago, in 2018, it amounted to 783 million US dollars.
The technology of obtaining and processing information about distant objects using lidars (active optical systems, LiDAR – Light Identification Detection and Ranging – detection, identification and range determination using light) is a key technology. It allows you to create a 3D map of the surroundings for autonomous vehicles and wide areas of application of robotics. This new application uses high-power and large-sized GaAs laser devices with “edge emission” (EEL), which are also expected to give a large growth impulse for the market for photon GaAs wafers. In 2024, the EEL market is expected to grow to 5,100 million USD, while in 2018 it was 2,500 million USD.
The IR LED sector on GaAs substrates is expected to show strong growth. GaAs-based infrared LEDs used in medical sensors for blood pressure and blood sugar, as well as sensors for recognizing gestures in smartphones and cars, also make up a prominent segment of the growing market.
In the future, in analyzing the applications of GaAs, for definiteness, we will single out the traditional visible-band LEDs into a separate category, and we will classify VCSEL-, EEL-, IR- and other emitters as “optoelectronics”.
Thermal imaging devices with photodetectors in quantum wells
The growing demand for infrared systems, caused by both military and civilian applications, will cause the growth of the global market for thermal cameras in the coming years. The market for thermal chambers for military and security applications, analysts predict, will exceed 2.4 billion USD by 2023, due to increasing security concerns. The use of infrared systems of the short-wave infrared range of the spectrum (0.9–1.7 μm) required the cooling of devices during their operation. This led to a significant expansion of their areas of application led to the appearance of cooled matrix photodetector devices (MFPs) based on and quantum wells (QWIP) (Fig. 5). Table 2 gives a brief overview of the IR modules of some foreign and domestic manufacturers with cooled MFPs on GaAs-based quantum wells.
GaAs MARKET DEVELOPMENT AFTER2017
For the GaAs DM market, analysts forecast 21% annual growth, which will yield more than half the volume of GaAs wafers by 2023. Speaking in financial terms about the general market for GaAs wafers, it is expected that the market, amounting to 260 million USD in 2019, will demonstrate an annual growth rate of 4.5% in the next 5 years, and will reach 330 million USD in 2024. The market growth dynamics in physical units (million units) is shown in Fig. 6.
GaAs manufacturers in the world and in Russia and existing business models
The main manufacturers of GaAs products (ingots, plates and epitaxial layers) are: Freiberger Compound Materials, AXT, Sumitomo Electric, China Crystal Technologies, Shenzhou Crystal Technology, Tianjin Jingming Electronic Materials, DOWA Electronics Materials, II–VI Incorporated, IQE Corporation and Wafer Technology In the field of bulk crystal supply, GaAs, Sumitomo Electric, Freiberger Composite Materials and AXT are leading the market with a total market share of about 95%.
Until recently, several small manufacturers of gallium arsenide single crystals of various forms of ownership remained in Russia, which together could satisfy most of the domestic needs for this material. However, in 2007, the production of single crystals in CJSC “Elma-Malakhit” (Zelenograd) was liquidated, which produced single crystals of undoped semi-insulating and doped GaAs using LEC technology. In 2008, the story of the existence of two other companies that grew GaAs crystals ended in the same way – OJSC “Research Institute of Materials of Electronic Technology” (Kaluga), which produced single crystals of doped GaAs using LEC technology, and LLC “Girmet” (Moscow), which produced single crystals according to VDC technology. Currently, gallium arsenide single crystals in Russia are manufactured by JSC “Giredmet: (Moscow, Rosatom Group enterprise) using the LEC method and by LLC “Lassard” (Obninsk) using the VDC method. Today JSC “Giredmet” and LLC “Lassard” are implementing investment projects aimed at developing GaAs technology. Also, in 2019, the production of heterostructures based on gallium arsenide was launched. JSC “Screen – Optical systems”, based on the development of the A. V. Rzhanov Institute of Semiconductor Physics (ISCP) of the SB of RAS, commissioned a molecular beam epitaxy (MBE) unit .
Since new laser applications dictate very high technical requirements for GaAs wafers, which are constantly being tightened, analysts believe that the WNK method will be dominant in this sector, and the mentioned players will retain their technical advantage for at least another 3–5 years. Chinese GaAs plate suppliers such as Violent Materials, which have captured part of the DM market from leading suppliers, are expected to increase their share.
As for the production of GaAs epitaxial structures and devices based on GaAs, various business models exist there (Fig. 7). The GaAs LED market is mostly vertically integrated, with well-established integrated device manufacturers such as Osram, Sanan, Epistar and Changelight. Over the past few years, the GaAs epitaxial structure sector has gone through great consolidation, leaving four major players left: IQE, VPEC, Sumitomo Chemicals (including Sumitomo Chemical Advanced Technologies and SCOCS) and IntelliEPI.
The main engine for the development of the GaAs market is photonics. In the medium and long term, global markets for GaAs wafers and epitaxial structures will grow. The GaAs wafer market is expected to reach 1.3 billion USD by 2023, with an annual growth rate of 11.5%. At the moment, the Russian market for semiconductor compounds for the development of photonics and the electron-component base (GaAs and others) has a small volume. At the same time, there is an understanding that in order to create a modern electronic component base in Russia, it is necessary to develop the production of raw materials . It also seems that, if we talk about the development of GaAs in Russia, first of all, it is necessary to develop technologies for VDC production of single crystals and epi-ready GaAs wafers.
Kulchitsky Nikolai Alexandrovich, Doctor of Technical Sci., e-mail: firstname.lastname@example.org, Chief Specialist, SSC RF, JSC Orion Scientific-Production Association, Moscow, Russia.
ORCID ID: 0000-0003-4664-4891
Naumov Arkady Valerievich, engineer-analyst, ASTROHN Technology Ltd,
https://astrohn.ru, Lytkarino, Moscow region, Russia.
Startsev Vadim Valerievich, Cand. of Technical Sciences, ASTROHN Technology Ltd, https://astrohn.ru, Lytkarino, Moscow region, Russia.
ORCID ID: 0000-0002-2800-544X