Growth and photoreflectance characterization of GaAs impact ionization avalanche transit time diodes

The organometallic vapor phase epitaxial growth of GaAs double-drift Read impact ionization avalanche transit time diodes where the p-type layers were doped with carbon is described. Ka-band oscillation testing yielded average performance of 3.5 W with 16% efficiency for pulse lengths >1 μs and 10.5 W with 13% efficiency for pulse lengths <1 μs; these RF performances are similar to conventionally grown vapor phase epitaxy IMPATTs where the p-type dopant was zinc. Photoreflectance spectra obtained from diode structures were found to be dominated by the electric field in the avalanche region and hence are sensitive to the amount of charge in the doping spikes that determine the electric field in that region.     

Influence of avalanche buildup time in TRAPATT diodes

Device equations for TRAPATT operation have been solved in a closed loop for optimization over the punch-through factor. Design triangles for various frequencies show design space for TRAPATT operation with optimized design near the apex of the triangles, and illustrate why it will be difficult to operate TRAPATT diodes at 20 GHz or higher.     

Bulk leakage in avalanche diodes due to silicon-metallization reactions

The results of heating TiAu and TiMoAu layers on silicon at 300°C in air are reported. Silicon is found to diffuse into the Au while Mo is found to act as a temporary barrier. The transport of Au and Si is responsible for a certain type of excess leakage in TRAPATT diodes.     

Controlled oxygen incorporation in indium gallium arsenide and indium phosphide grown by metalorganic vapor phase epitaxy

The defect engineering in metalorganic vapor phase epitaxy In_xGa_1-xAs and InP by controlled oxygen doping using diethyl aluminum ethoxide (DEALO) was developed in this study. DEALO doping has led to the incorporation of Al and O, and the compensation of shallow Si donors in In_xGa_1−xAs: Si with 0 ≤ x ≤ 0.25. With the same DEALO mole fraction during growth, the incorporation of Al and O was found to be independent of x, but the compensation of Si donors decreases with increasing In content. Deep level transient spectroscopy analysis on a series of In_xGa_1-xAs: Si. samples with 0 ≤ x ≤ 0.18 revealed that oxygen incorporation led to a set of deep levels, similar to those found in DEALO doped GaAs. As the In composition was increased, one or more of these deep levels became resonant with the conduction band and led to a high electron concentration in oxygen doped In_0.53Ga_0.47As. Low temperature photoluminescence emission measurements at 12K on the same set of samples revealed the quenching of the near-band edge peak, and the appearance of new oxygen-induced emission features. DEALO doping in InP has also led to the incorporation of Al and O, and the compensation of Si donors due to oxygen-induced multiple deep levels.     

The effect of photogenerated carriers on the mean time delay for avalanche breakdown in p-n junctions

Avalanche breakdown in p-n junctions is preceded by a delay time between application of an overvoltage and the actual initiation of an avalanche discharge. The mean of this delay time has been studied as a function of photogeneration in p-n junction devices. Results agree well with McIntyre's theory of breakdown probability. The data further indicate that the probability of any given carrier initiating breakdown is independent of carrier concentration over the three orders of magnitude investigated.     

Prospects of gallium nitride double drift region mixed tunneling avalanche transit time diodes for operation in F, Y and THz bands

The potential of GaN as a wide band gap semiconductor is explored for application as double drift region mixed tunneling avalanche transit time (MITATT) diodes for operation at 120 GHz, 220 GHz and 0.35 THz using some computer simulation methods developed by our group. The salient features of our results have uncovered some peculiarities of the GaN based MITATT devices. An efficiency of more than 20% right up to a frequency of 0.35 THz (from the GaN MITATT diode) seems highly encouraging but a power output of only 0.76 W is indicative of its dismal fate. The existence of a noise measure minimum at the operating frequency of 0.35 THz is again exhilarating but the value of the minimum is miserably high i.e. more than 33 dB. Thus, although GaN is a wide band gap semiconductor, the disparate carrier velocities prevent its full potential from being exploited for application as MTATT diodes.     

Calculation of the switching time in junction diodes

Simple expressions for the switching time of junction diodes are derived. The expressions are valid for all possible values of the switching current and of the width to diffusion length ratio. Charge storage in both neutral regions are taken into account. The validity of published approximations is extended. Similar calculations can be important for studying the switching behaviour of a bipolar transistor, taking the charge stored in the collector into account.     

Operation of avalanche diodes as c.w. amplifiers at fractions of the transit frequency

The operation of an avalanche diode as a self-pumped parametric amplifier at low current densities is described. Gains of up to 15 dB are obtained at frequencies of the order of one-quarter of the transit frequency, while the diode is providing its own pump at three-quarters of that frequency. A theory based on utilising a Read-diode approximation to the device is used to calculate the response of such an amplifier, and good agreement is found for both the gain and saturation characteristics of the device.     

Measurement of carrier-concentration profiles in epitaxial indium phosphide

A technique is described for measuring carrier-concentration profiles of vapour-deposited epitaxial indium phosphide using the capacitance/voltage characteristics of a reverse biased metal-insulator-semiconductor diode. Profiles of layers grown on chromium and tin-doped substrates are presented. The effect of dopant type on the sharpness of electrical interfaces is discussed.     

Diffusion of hot electrons in n indium phosphide

The diffusion-conefficient/field characteristic has been calculated for n indium phosphide. The resulting curves show several pearks and minima. The origin of these features is discussed.     

Modes of avalanche oscillations in silicon diodes

A computer program which includes both electronic and thermal processes has been used to study avalanche oscillations in a diode which is punched through only well above breakdown. IMPATT, relaxing avalanche, and MULTIPATT oscillations have been studied. The MULTIPATT mode is shown to be a superpesition of transit-time oscillations upon a relaxation oscillation. It is postulated that the TRAPATT mode is initiated by the IMPATI mode via the MULTIPATI mode. The frequency of the IMPATT oscillations was found to vary with the square root of the current over a factor of 100 in current. For parallel operation of TRAPATT diodes, it is shown that nonpunched-through diodes should be used.     

The influence of capture of the injected current carriers on the characteristics of baritt diodes

The two-terminal impedance characteristics of a semiconductor punch-through structure are examined for operation under low field conditions, i.e. constant mobility, and for trap levels in the band gap of the semiconductor. It is shown, that the negative resistance effects are increased under the influence of trapping of injected carriers. With the increase of the concentration of traps the dynamic negative resistance also increases in absolute value, but the frequency band, where dynamic negative resistance takes place, narrows and is displaced to a lower frequency.     

Array grating lobes due to periodic phase, amplitude, and time delay quantization

Simple approximate formulas and generalized curves to evaluate the grating lobe levels of various kinds of contiguous subarrays with uniform illumination within each subarray are presented. The cases considered include phase quantization due to discrete phase shifters, amplitude taper at subarray input ports and time delay at the subarray input ports. In addition, the work is generalized to include certain cases of quantized phase or time delay at the input ports in addition to amplitude taper at subarray input ports.     

Annealing of damage in Se+-implanted indium phosphide

The production and annealing of damage in (100) InP implanted with Se⁺ ions at 77 K, room temperature and 180°C have been studied by channeling and differential Hall measurements. For ion energies from 100 to 400 keV, fluences of 10¹⁴ and 10¹⁵ cm^?2 produce amorphous layers which extend to the surface in samples implanted at 77 K or room temperature, while the samples implanted at 180°C remain crystalline. According to the channeling measurements, amorphous layers less than 2000 Å thick produced by either 77 K or room-temperature implants are completely reordered by annealing at 750°C for 10 min, while the post-anneal residual disorder of thicker layers is linearly dependent on the initial amorphous layer thickness. After annealing, samples implanted at 180°C have higher sheet carrier concentrations and mobilities but considerably broader carrier concentrations than samples similarly implanted at either 77 K or room temperature, even when the amorphous layers in the latter samples are completely reordered. It is considered that for most applications heated implants should be used to avoid the formation of amorphous layers.     

Shallow and selective diffusion of zinc in indium phosphide

Diffusion experiments at 670–720°C from doped silica films into n-type InP are described. The diffusant is Zn. The films are spun on from emulsions and carefully solidified. The diffused samples were investigated mostly by stain etching and additionally by C-V and break-down measurements on Schottky diodes, by four-point-probe and Hall measurements. Homogeneous diffusion fronts were obtained. From the square-root dependence of the diffusion depth on the diffusion time and from the measurements mentioned before an errorfunction-complement type of diffusion profile can be inferred. The evaluation of the results then gives a diffusion coefficient of (2 ± 1) × 10^?10 cm²/s and a total Zn concentration at the surface of about 2 × 10¹⁸ cm^?3. It is demonstrated that with conventional photolithography selective diffusions can be performed.     

掺Fe元素的InP晶体中扩展位错的运动

利用LEG法制备掺Fe0.03wt.%的InP晶体。样品观察在JEM-4000EX高分辨电镜上进行,电压为400kV,点分辨率为0.19nm(Cs=1mm),电镜中电子束产生的辐照为2.5×103e/cm2s。InP晶体是立方闪锌矿结构,空间群为F43m,单胞参数为a=0.5868nm。图1是InP扩展螺位错在[110]方向投影的高分辨像。图中亮点对应原子位置。很明显,一层(111)原子被抽去。图中用黑点标出了扩展位错的螺型分量。扩展位错包括两个Burgers矢量为1/6[211]和1/6[121]的Shockley不全位错,其间是内禀层错。扩展位错之间的距离为17.9nm。层错能可根据下式计算[1]:R=μb2(2-3V)/8πd…     

Observation of high-field domains in n type indium phosphide

Transit-time oscillations involving dipole domains in long samples of InP are reported. Impact ionisation can occur within the domains. The domain velocity was determined by probe measurements. Under certain circumstances, oscillations at frequencies much higher than the transit-time frequency were observed. Conclusions concerning the velocity/field characteristic are presented.     

Automatic electrochemical profiling of carrier concentration in indium phosphide

The technique of carrier concentration profiling over a wide doping and depth range, via automatic C/V analysis and disolution at an electrolytic Schottky barrier, is here demonstrated for indium phosphide