Electron transport in avalanching GaAs diodes

Magnetoresistance measurements on avalanching GaAs diodes lead to an estimate of 1.6 × 10^-15sec for the scattering time of avalanching electrons at 300K. This is consistent with the time recently calculated by Monte Carlo techniques. It confirms that impact ionization by electrons in GaAs is initiated by carriers that make several collisions in the process rather than by ballistic carriers which impact ionize without any interaction with phonons.     

Electron drift velocity in avalanching silicon diodes

The differential resistance of an avalanching p⁺nn⁺junction is used to obtain the electron drift velocity at electric fields where significant avalanching is occurring (2 × 10⁵< E < 4 × 10⁵V/cm). The velocity is also obtained as a function of temperature and is consistent with energetic phonon scattering.     

Millimeter-wave amplification by avalanching varactor diodes

Transmission-type amplifiers in the 50-GHz band were constructed with Ge silver-bonded varactor diodes biased in the avalanche condition. A transmission gain of 4 to 6 dB was stably obtained. The bandwidth was about 230 MHz.     

雪崩PIN二极管中的电流丝运动

The motion of current filaments in avalanching PIN diodes has been investigated in this paper by 2D transient numerical simulations.The simulation results show that the filament can move along the length of the PIN diode back and forth when the self-heating effect is considered.The voltage waveform varies periodically due to the motion of the filament.The filament motion is driven by the temperature gradient in the filament due to the negative temperature dependence of the impact ionization rates.Contrary to the traditional understanding that current filamentation is a potential cause of thermal destruction,it is shown in this paper that the thermally-driven motion of current filaments leads to the homogenization of temperature in the diode and is expected to have a positive influence on the failure threshold of the PIN diode.     

Measurement of the electron drift velocity in avalanching GaAs diodes

The scattering-limited drift velocity vsnof electrons in an avalanching GaAs diode is estimated by measuring the space-charge resistance. The result shows a lower value of vsn(5.7 ± 0.3) × 10⁶cm/s than the generally accepted value 8 × 10⁶cm/s at room temperature. The temperature dependence of vsnis also measured.     

Measurements on light emission and current distribution in avalanching epitaxial diodes

Silicon diodes built in epitaxial layers of varying parameters were found to exhibit two distinct modes of light-emission dependence on avalanching current prior to secondary breakdown. The modes depend on whether the depletion layer extends to the substrate interface prior to avalanche or not. Current distribution is inferred from the light curve and a possible mechanism leading to the secondary breakdown is suggested.     

Triggering phenomena in avalanche diodes

The operation of a small area p-n junction diode above the breakdown voltage is analyzed. A new formulation in terms of ionization probability is used to derive the rate of turn-on of current in such structures. Two differential equations are given which may be used to compute the probability that a carrier swept into or generated within the space-charge region triggers avalanche breakdown. For a 27-V n⁺-p diode biased 1 V above breakdown, this probability is close to 0.5 for an electron entering from the p side, or 0.1 for a hole entering from n side. Experimental measurements are in good agreement with the theoretical predictions.     

Modeling of steady-state optical phenomena in transistors and diodes

A lumped model is derived for photodiodes and phototransistors from which steady-state spectral properties, such as quantum efficiency, can be determined. The model is derived in a manner such that its utility extends to regions of any length ω that is, there is noomega/Lll1restriction, whereLrepresents the minority-carrier diffusion length in the region. The validity of the resulting model is demonstrated by showing that the lumped model predicts the empirically measured quantum efficiency of planar photodiodes to within 10 percent.     

High-frequency silicon-on-sapphire IMPATT oscillator

Epitaxially grown silicon-on-sapphire (SOS) monolithic integrated IMPATT oscillators were fabricated and tested. One diode was successfully operated under pulsed conditions yielding 10-mW peak power output at 13.8 GHz. This experiment serves to demonstrate the feasibility of silicon-on-sapphire monolithic integration at microwave frequencies.     

Subthreshold conduction in silicon-on-sapphire transistors

The subthreshold conduction in silicon-on-sapphire MOS transistors has been studied both theoretically and experimentally. A simple model to describe the subthreshold conduction current for both thick films and thin films is derived in terms of charges in the silicon and charges at the silicon-silicon dioxide and silicon-sapphire interfaces. The model has been extended to cover short-channel transistors by application of charge conservation under the channel region. It is shown that the subthreshold conduction current for a SOS-MOS transistor has a form similar to that found in bulk transistors, but with modification of the terms due to the finite silicon film thickness and the unique geometry of the SOS-MOS transistor. The general form of the model has been confirmed by measurement of the subthreshold current on several hundred SOS-MOS transistors of different geometries manufactured by various companies.     

Bipolar junction transistors fabricated in silicon-on-sapphire

The effects of processing temperature on collector leakage current in bipolar junction transistors (BJTs) fabricated in silicon-on-sapphire (SOS) were examined. At low process temperatures (850 degrees C) a reduction of five orders of magnitude in the collector leakage current was observed. Excellent I-V characteristics were obtained on both NPN and PNP transistors fabricated at lower temperatures. Measured DC current gain beta for the NPN devices was 30, and that of the PNP devices was 40. Additionally, current mode logic (CML) circuits fabricated using these transistors exhibited well behaved DC switching characteristics.<>     

Avalanche phenomena in 4H-SiC p-n diodes fabricated by aluminum orboron implantation

Characteristics of p-n junction fabricated by aluminum-ion (Al⁺) or boron-ion (B⁺) implantation and high-dose Al⁺-implantation into 4H-SiC (0001) have been investigated. By the combination of high-dose (4×10¹⁵ cm^-2) Al⁺ implantation at 500°C and subsequent annealing at 1700°C, a minimum sheet resistance of 3.6 kΩ/□ (p-type) has been obtained. Three types of diodes with planar structure were fabricated by employing Al+ or B+ implantation. B ⁺-implanted diodes have shown higher breakdown voltages than Al⁺-implanted diodes. A SiC p-n diode fabricated by deep B+ implantation has exhibited a high breakdown voltage of 2900 V with a low on-resistance of 8.0 mΩcm² at room temperature. The diodes fabricated in this study showed positive temperature coefficients of breakdown voltage, meaning avalanche breakdown. The avalanche breakdown is discussed with observation of luminescence     

Detection of avalanching in submicrometer field-effect devices

In submicrometer field-effect devices, where large electric fields are produced in the channel region under normal biasing conditions, the presence and the onset of avalanching can be detected by the measurement of the noise power spectrum of the drain current at a frequency in the UHF range. This technique is illustrated by measurements on GaAs MESFET's.     

Characterization of silicon-on-sapphire IGFET transistors

Under dynamic operation conditions, the potential of the floating substrate in a silicon-on-sapphire (SOS) device is primarily controlled by the capacitive coupling of the substrate to other device terminals. However, a key parameter that plays a major role in defining that potential during switching is the avalanche multiplication current produced by the channel current carriers in the surface space charge region adjacent to the drain. A closed form expression is derived for the avalanche current, enabling the development of a nonlinear equivalent circuit model of the device. Comparison of measurements with device terminal characteristics, as well as the switching behavior of the device, shows good agreement.     

Digital isolation amplifier in silicon-on-sapphire CMOS

The design and fabrication results of a monolithic four-channel digital isolation amplifier in a 0.5 mum silicon-on-sapphire technology is reported. The isolation device is manufactured in a single die, taking advantage of the isolation properties of the sapphire substrate. The individual isolation channels can operate in excess of 40 Mbit/s using digital phase-shift-keying modulation. Modulation of the input signal is used to increase immunity to errors at low input data rates. The device can tolerate ground bounces of 1 V/mus and isolate more than 800 V     

Non uniform recombination in thin silicon-on-sapphire films

Recombination parameters of SOS films are deduced from the study of the magnetoconcentration effect in double-injecting structures. The method of measurement is based on an original theory succintly developed; it takes into account general SRH bulk and surface recombination laws; moreover inhomogeneous distributions of recombination centers are considered.Experimental results (current-voltage characteristics of such “magnetodiodes”), when analysed according to the proposed method, lead to more realistic values of the global recombination parameters (τ_v, S₁, S₂) of the SOS film. It is proved, for example, that the previous simplified analysis overestimates the carrier recombination velocity on the Si-Al₂O₃ surface. On the contrary our method gives both a moderate value for this recombination velocity and a lower carrier lifetime near the Sapphire interface, which well agrees with the continuity of recombination rates at the surface and in the underlying bulk; the higher recombination region is found to be 100–1000 Å thick.     

The frequency response of avalanching photodiodes

The Townsend equations for avalanche breakdown in back biased p-n junctions may be derived from the transport equations for semiconductors. Integral solutions of the time independent equations are well known. An integral solution of the time dependent equations is given for multiplication by one carrier only. An exact solution is given for multiplication by two carriers with equal ionization coefficients in a constant junction field. The Townsend equations are nonlinear because of space charge effects. It is shown, however, that the nonlinearity, which imposes an upper limit on the current multiplication possible, is not important until the total multiplied current approaches the space charge limited current for the junction. Assuming multiplication is due to one carrier, frequency response curves are calculated for constant and linear junction fields and for a generation rate, due to photon absorption, which is either uniform or given by a delta function at the junction boundary. The curves indicate a relatively slight dependence of the frequency response on multiplication. Frequency response curves are also given for multiplication by both carriers with equal ionization coefficients when the junction field is constant. In this case the frequency response decreases continuously as the multiplication is increased. For multiplication by two carriers with unequal ionization coefficients, the frequency response is independent of multiplication until the product of the multiplication and the ratio of the ionization coefficients approaches one. Thereafter the frequency response decreases with multiplication.