In the past several years, research in each of the wide‐band‐gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high‐temperature electronics and short‐wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high‐power operation. The present advanced stage of development of SiC substrates and metal‐oxide‐semiconductor technology makes SiC the leading contender for high‐temperature and high‐power applications if ohmic contacts and interface‐state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high‐temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra. Blue SiC light‐emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN‐based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short‐wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN‐based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe‐based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide‐band‐gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

Large‐band‐gap SiC, III‐V nitride, and II‐VI ZnSe‐based semiconductor device technologies

Wide bandgap GaN has long been sought for its applications to blue and UV emitters and high temperature/high power electronic devices. Recent introduction of commercial blue and blue-green LED's have led to a plethora of activity in all three continents into the heterostructures based on GaN and its alloys with AlN and InN. In this review, the status and future prospects of emerging wide bandgap gallium nitride semiconductor devices are discussed. Recent successes in p-doping of GaN and its alloys with InN and AlN, and in n-doping with much reduced background concentrations have paved the way for the design, fabrication, and characterization of devices such as MESFET's, MISFET's, HBT's, LED's, and optically pumped lasers. We discuss the electrical properties of these devices and their drawbacks followed by future prospects. After a short elucidation of materials characteristics of the nitrides, we explore their electrical transport properties in detail. Recent progress in processing such as formation of low-resistance ohmic contacts and etching is also presented. The promising features of quarternaries and double heterostructures in relation to possible current injection lasers, LED's, and photodetectors are also elaborated on. >

Emerging gallium nitride based devices

Progress and prospects of group-III nitride semiconductors

Compact and efficient sources of blue light for full color display applications and lighting eluded and tantalized researchers for many years. Semiconductor light sources are attractive owing to their reliability and amenability to mass manufacture. However, large band gaps are required to achieve blue color. A class of compound semiconductors formed by metal nitrides, GaN and its allied compounds AIGaN and InGaN, exhibits properties well suited for not only blue and blue-green emitters, but also for ultraviolet emitters and detectors. What thwarted engineers and scientists from fabricating useful devices from these materials in the past was the poor quality of material and lack of p-type doping. Both of these obstacles have recently been overcome to the point where highluminosity blue and blue-green light-emitting diodes are now available in the marketplace.

https://science.sciencemag.org/content/sci/267/5194/51.full.pdf

High-luminosity blue and blue-green gallium nitride light-emitting diodes.

Reactive‐ion molecular‐beam epitaxy has been used to grow epitaxial hexagonal‐structure α‐GaN on Al2O3(0001) and Al2O3(0112) substrates and metastable zinc‐blende‐structure β‐GaN on MgO(001) under the following conditions: growth temperature Ts=450–800 °C; incident N+2/Ga flux ratio JN+2/JGa=1–5; and N+2 kinetic energy EN+2=35–90 eV The surface structure of the α‐GaN films was (1×1), with an ≊3% contraction in the in‐plane lattice constant for films grown on Al2O3(0001), while the β‐GaN films exhibited a 90°‐rotated two‐domain (4×1) reconstruction Using a combination of in situ reflection high‐energy electron diffraction, double‐crystal x‐ray diffraction, and cross‐sectional transmission electron microscopy, the film/substrate epitaxial relationships were determined to be: (0001)GaN∥ (0001)Al2O3 with [2110]GaN∥[1100]Al2O3 and [1100]GaN∥[1210]Al2O3, (2110)GaN∥(0112)Al2O3 with [0001]GaN∥[0111]Al2O3 and [0110]GaN∥[2110]Al2O3, and (001)GaN∥(001)MgO with [001]GaN∥[001]MgOFilms with the lowest e

Heteroepitaxial wurtzite and zinc‐blende structure GaN grown by reactive‐ion molecular‐beam epitaxy: Growth kinetics, microstructure, and properties

The growth and characterization of AlN and GaN on GaAs are presented. Trimethylgallium (TMG) and trimethylaluminum (TMA) were used as group III sources and hydrazine as a nitrogen source. It was found for both nitrides that mass-transport-limited growth took place at high temperature, and that at low temperature the surface catalyzed decomposition of respective metalorganics manifested itself. Deposition of AlN film was observed at as low as 220°C and that of GaN at 450°C both on GaAs substrates. A distinct proof of cubic-form GaN grown on GaAs is obtained from results of the X-ray precession measurement. The direction of GaN on (100) GaAs, however, is slightly tilted from that of the substrate. It is speculated that this tilt results from the very large lattice-mismatch existing between GaN and GaAs.

Low Temperature Growth of GaN and AlN on GaAs Utilizing Metalorganics and Hydrazine

A GaN crystal film having a mask patterned in a stripe for forming multiple growing areas on a sapphire substrate and coalesced GaN crystals covering the mask dividing the areas, grown from the neighboring growing areas, comprising defects where multiple dislocations along with the stripe are substantially aligned with the normal line of the substrate, in the crystal areas over the mask, and dislocations propagating in substantially parallel with the substrate surface while, in the vicinity of the areas where the crystals are coalesced over the mask, propagating substantially in the normal line of the substrate surface, and a manufacturing process therefor. According to this invention, there can be provided a GaN crystal film in which strain, defects and dislocations are reduced and which tends not to generate cracks.

GaN crystal film, a group III element nitride semiconductor wafer and a manufacturing process therefor

For the undoped semi-insulating LEC GaAs crystal, microscopic inhomogeneity was investigated on the fixed position by using cathodoluminescence (CL), secondary ion mass spectrometry (SIMS), X-ray topography (XRT) and scanning leakage current measurement (IL). Microscale fluctuations observed in these measurements were attributed to the cellular dislocation structures. It was suggested that the impurity gettering effect of dislocation plays an important role in the semi-insulation mechanism in GaAs crystal. Carriers are inactive in the boundary region of cell structures but are active in the inner region of cell structures.

Role of Dislocations in Semi-Insulation Mechanism in Undoped LEC GaAs Crystal

New Stripe Geometry Laser with High Quality Lasing Characteristics by Horizontal Transverse Mode Stabilization : A Refractive Index Guiding with Zn Doping

Two types of cubic and hexagonal GaN films were deposited on (001) GaAs substrates. The film structure proved to be controlled by GaAs pretreatments. By performing a N2H4 (hydrazine) pretreatment of GaAs substrates, the GaN films, which were otherwise hexagonal similarly to ordinary films on sapphire substrates, became cubic. A surface cubic nitride layer was found to be formed on the pretreated GaAs by a RHEED (reflection high-energy electron diffraction) observation, which is thought to be the substantial substrate for the following growth of a cubic GaN film.

Yoshishige Matsumoto

Papers

Low Temperature Growth of GaN and AlN on GaAs Utilizing Metalorganics and Hydrazine

GaN crystal film, a group III element nitride semiconductor wafer and a manufacturing process therefor

Role of Dislocations in Semi-Insulation Mechanism in Undoped LEC GaAs Crystal

New Stripe Geometry Laser with High Quality Lasing Characteristics by Horizontal Transverse Mode Stabilization : A Refractive Index Guiding with Zn Doping

Structure Control of GaN Films Grown on (001) GaAs Substrates by GaAs Surface Pretreatments