Mobility degradation and transferred electron effect in gallium arsenide and indium gallium arsenide

The effect of mobility degradation on the intervalley transfer of electrons in gallium arsenide and indium gallium arsenide is studied. A considerable degradation of the mobility at high electric fields takes place for valleys with high low-field ohmic mobility. The momentum relaxation time τ = m^*µ/e is found to degrade with high electric field, giving the impression of high collision broadening at high electric fields. Similar degradation is expected for the mean free path. The relationship of the high-field transport in terms of ohmic transport parameters is elaborated to explain the transferred electron effect.     

Spontaneous oscillations in gallium arsenide field effect transistors

We present results of experiments and numerical simulations designed to reveal the presence of spontaneous oscillations arising from negative differential mobility effects in gallium arsenide field effect transistors. The measurements include d.c. and pulsed current/voltage vs temperature characterization, sampling scope measurements, spectral analysis to 40 GHz and observation of light emission. The simulation is a time dependent large signal transient analysis arising from a fully two-dimensional solution of the self-consistent potential and charge within the device.     

Self-Diffusion in gallium arsenide

The self-diffusion of arsenic in gallium arsenide has been studied over the temperature range 1000 to 1075δC using radiotracer techniques.⁷⁶As was diffused into GaAs samples at known arsenic pressures in sealed capsules. After diffusion, layers were removed from the surface using anodic oxidation followed by oxide dissolution. Diffusion profiles were obtained by measuring the⁷⁶As concentration in each sectioned layer by γ-radiation counting. Diffusion coefficients at P_{As 2} = 0.75 atm and over the temperature range 1000 to 1050δC were found to be 5.2 × 10^-16cm²s^-1 to 1.5 × 10^-15 cm²s^-1, leading to an activation energy of the order of 3.0^± 0.04 eV and a pre-exponential factor of 5.5 × l0^-4 ± 2.4 × 10^-4 cm²s^-1. Diffusion coefficients at P_{As 2} =3.0 atm were found to be 5.5 × 10^-15 and 9.8 × 10^-16 cm² s^-1 at 1050 and 1075δC, respectively. Results are discussed in terms of native point defect equilibria with the arsenic gaseous phase, and with respect to other work. It is deduced from our observed arsenic pressure dependence of the arsenic diffusivity that the most likely diffusion mechanism     

Phosphorus diffusion in gallium arsenide

The formation of monocrystalline GaAs_1?xP_x by the solid state diffusion of phosphorus into monocrystalline GaAs at a phosphorus pressure of 35 atm has been confirmed by X-rays and reflectivity measurements. Phosphorus distribution in GaAs specimens diffused in the temperature range 800–1100°C has been determined by reflectance studies. The diffusion coefficient and the activation energy computed from the known phosphorus distributions in the diffused specimens are found to depend on the content of phosphorus in the diffused region. The variation of the depth of GaAs_1?xP_x-GaAs junction with time (at a fixed temperature, 1000°C) and temperature (for a fixed time, 24.5 hr) has been studied.     

Chromium diffusion in gallium arsenide

Chromium diffusion in GaAs was studied by measuring the thickness of high-resistivity layers formed during diffusion of chromium (a deep acceptor) in n-GaAs. The dependence of the chromium diffusivity in GaAs on the temperature, arsenic-vapor pressure, conductivity type, and carrier density was determined. The temperature dependence of the diffusivity is described by the Arrhenius equation with the parameters D₀=8×10⁹ cm²/s and E=4.9 eV. The dependence of the diffusivity on the arsenic-vapor pressure is described by the expression \(D \propto P_{As_4 }^{ - m} \), where m≈0.4. The experimental data obtained are interpreted in terms of the concept of the dissociative mechanism of migration of Cr atoms in GaAs.     

High-peak-power gallium arsenide oscillators

The Gunn effect appears to be the first semiconductor phenomenon capable of generating high peak power at microwave frequencies. This paper describes some preliminary experimental work in which gallium arsenide oscillators were made and operated in the range from 725 to 2000 Mc/s. Two device fabricating techniques and two circuit configurations have been found useful. Individual devices can be made to tune over a 25 percent range with a single capacitor adjustment. Voltage tuning of a few percent is generally observed. The highest peak power observed so far is 205 watts at 1540 Mc/s, obtained from two GaAs wafers operating in parallel. A large number of single devices have worked at power levels between 40 and 100 watts, and efficiencies from 3 to 9 percent. The phenomenon shows considerable promise for moderate power pulsed microwave oscillators. Predictable devices and useful design techniques will be delayed until the reproducibility and temperature variations of the raw material are brought under control.     

Photoreflectance characterization of gallium arsenide

A novel method of noncontact and nondestructive characterization by photoreflectance spectroscopy is validated on bulk and epitaxial GaAs single crystals with different levels of doping. The method is used to simultaneously determine the surface electric field and free-carrier concentration. Close agreement is observed between photoreflectance-spectroscopy and Hall-effect measurements.     

Breakdown characteristics of gallium arsenide

This paper presents a comparison of the experimentally measured breakdown characteristics of high-purity gallium arsenide epitaxial layers with the theoretical calculations reported in the literature. The experimental data has been obtained by forming gold Schottky barrier diodes on material grown by using two different liquid phase epitaxial growth techniques. Good agreement is observed between the measured data and the breakdown voltages calculated by Lee and Sze[4] for     

High-temperature irradiation of gallium arsenide

Deep level transient spectrocopy was used to investigate the introduction of P2 and P3 centers into n-type epitaxial layers of GaAs as a result of exposure to 4-MeV electrons in the temperature range 380–550 °C. It is shown that the rate at which the centers are introduced into the layers is independent of temperature in this range. The P2 center concentration is proportional to D ^0.7, whereas for the P3 center this function is D ^0.5, where D is the electron dose. Fiz. Tekh. Poluprovodn. 31, 1234–1235 (October 1997)     

Deep centers in neutron-transmutation-doped gallium arsenide

Three electron traps at 0.21, 0.27 and 0.68 eV below the conduction band edge and a hole trap at around 0.11 eV above the valence band edge have been observed in neutron-transmutation-doped liquid-phase-epitaxial GaAs. All four levels are undetectable after a heat treatment at 600°C for 5 min.     

Low-frequency noise in gallium arsenide structures

This work reports the study of low-frequency electrical noise in Gallium Arsenide (GaAs) resistor and MESFET structures. The current and frequency dependence of the noise was found to indicate the presence of at least two physical mechanisms. The identified mechanisms are time constant related diffusion noise and trapping/detrapping by a mechanism having a distribution of time constants with a lower limit on the distribution.     

Acoustic-surface-wave propagation on gallium arsenide

Measurements of surface-wave parameters on the {100} plane of gallium arsenide are presented. Measurements around the 100 MHz region reveal three types of wave, whose velocities are compared with theoretical predictions. Some estimates of the coupling coefficient and beam steering are also made.     

Metal contacts to gallium arsenide

In this paper, some aspects that determine the properties of Schottky and ohmic contacts to GaAs are discussed. For Schottky barrier diodes (SBD), we present results of a comprehensive study involving 41 different metals. We pay special attention to Ru and show that its thermal and chemical stability makes it ideal for use in devices operating above room temperature and for experiments involving annealing. Further, we discuss the effect of different metallization methods on SBD properties and show that methods which use energetic particles, such as electron beam deposition and sputter deposition, often result in inferior SBD properties—the consequence of electrically active defects introduced by the energetic particles at and close to the semiconductor surface. The advantages of using Ru as contact material to GaAs are that it forms high quality, thermally stable Schottky contacts to n-GaAs and thermally stable ohmic contacts with low specific contact resistance to p-GaAs. The versatile applicability of Ru contacts makes them extremely important for future use in devices such as heterojunction bipolar transistors and solid state lasers.     

High average-power gallium arsenide illuminators

Average optical output powers in the 5-watt range from GaAs arrays emitting peak powers of 500 watts at 10 kHz have been built for ground illumination and ranging. The thermal optical design for accomplishing this performance at 77°K is shown. The arrays described are3frac{1}{2}inches in diameter and weigh 2 pounds. Overall efficiencies approaching 30 percent at 101°K and 40 percent at 77°K have been achieved. Without adjustment other than lens focus, overall tolerances of 0.1° in alignment have been shown by the use of straight, rectangular light pipes. Output beams of2deg times 6deghave been obtained with beam uniformities of less than 10 percent.     

The diffusion of silicon in gallium arsenide

The rate of diffusion of silicon from a sputtered film of silicon into gallium arsenide has been studied as a function of the ambient arsenic pressure at 900 and 1000°C. The diffusion appears to be non-Fickian. The saturated surface concentration of silicon in diffused layers is about 0·3 wt per cent and the average electron concentration of the layers is about 5 × 10¹⁸ cm⁻³. Silicon has been used as an emitter diffusant in a double diffused GaAs transistor.     

Dielectric constant of semi-insulating gallium arsenide

Results are given on precision measurements of the relative dielectric constant of high-purity semi-insulating gallium arsenide. Using this and other data, it is concluded that the value is within about 0.5% of 12.9, and does not vary significantly between zero frequency and at least 70 GHz.     

Gettering of impurities from gallium arsenide

Impurities have been gettered from gallium arsenide using a glass surface layer. Mobility has been found to increase by a factor of two to three. Injection-laser threshold current density at 77K reduced from 750Acm?2 to 425Acm?2.