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In this work, we have decoupled the radiative and nonradiative contributions to recombination by developing analytical models to fit observed non-monoexponential photoluminescence decay and bulk-lifetime temperature-dependence, which has enabled absolute measurement of the effective radiative efficiency and characterization of the dominant defect in lightly doped GaAs samples grown using molecular-beam-epitaxy. The measured effective radiative efficiency values under low level injection conditions range from (88.9 ± 0.1)% and (81.2 ± 0.1)% at 77 K to (0.028 ± 0.001)% and (0.034 ± 0.001)% at 700 K, with 300 K values of (17.3 ± 0.1)% and (10.5 ± 0.1)% in the p-type and n-type samples, respectively. A common defect-signature is observed in the temperature-dependence of the nonradiative lifetime in samples of both doping types, and our measured parameters are consistent with characteristics previously measured for the EL2 defect using deep-level transient spectroscopy.

Sidegating in GaAs metal‐semiconductor field‐effect‐transistors (MESFETs) is widely attributed to space‐charge‐limited (SCL) conduction through the semi‐insulating (SI) substrate. But often sidegating is accompanied by low sidegate currents and occurs at sidegate voltages that are too small to initiate SCL conduction. We suggest that this is due to low‐level hole injection from a MESFET into the substrate. An analytical treatment of carrier, field, and potential distribution in a SI substrate under conditions of low‐level injection shows that an electric field overshoot may develop in the vicinity of the MESFET when hole injection occurs. This results in a large portion of the applied voltage being dropped across the channel‐substrate interface and, consequently, in sidegating. One result for short structures is the electric field outside the narrow region of overshoot is below the value expected for ohmic conduction. Consequently, over a wide range of applied voltages the field in most portions of the structure is below the critical value required for intervalley electron transfer.

The dynamics of hot minority carriers in p‐GaAs is calculated for doping concentrations in the range of 1.5×1017 cm−3 to 1.5×1018 cm−3. It is shown that the electron‐hole interaction increases the rate of dissipation of the excess energy of the minority carriers in the early stages of the process. However, this channel for energy dissipation becomes weaker as the cooling of the minority carriers proceeds, an effect more noticeable in the case of high doping levels. When the electron‐hole interaction is disregarded, the dissipation rate is always smaller for low doping concentrations.

Knowledge of both carrier bulk lifetime τb and surface recombination velocity S are necessary to analyze and model electron devices. In this paper, the analytical results of Luke and Cheng [J. Appl. Phys. 61, 2282 (1987)] are applied to examine excess carrier decay due to pulsed Gaussian optical excitation to extract values of τb and S under low level injection. The nondestructive, contactless measurement technique utilizes a visible pulsed laser pump beam and a CW infrared laser probe beam. Values for τb and S are obtained for a number of different Si samples. The effect of varying the pump beam frequency is examined. The technique is simple to use in the laboratory and the parameter extraction from the measured data is straightforward.

This paper presents an accurate and practical mathematical model of time-resolved photoluminescence (PL) response from silicon wafers generated by fast repetitive excitation pulses. The model is valid under low level injection condition and takes into account the depth dependence of carrier generation, diffusion, and surface recombination. Finite element analysis is employed for the carrier density and PL computations. By comparing computational results with results obtained from PC1D (a computer program solving fully coupled nonlinear equations for quasi-one-dimensional carrier transportation in crystalline semiconductor devices, especially focusing on photovoltaic devices), the validity of this method is confirmed. Early stage application and the limitations of this method have been studied, and future work has been proposed.

We present spatially resolved and injection dependent excess carrier lifetime measurements on silicon. At low level injection conditions an anomalous increase often interferes in such measurements. The origin of the anomalous increase is discussed. Assuming trapping as the origin, highly resolved images of trap parameters together with low level injection recombination lifetimes with strongly reduced trapping effects have been obtained. A theoretical model for infrared lifetime imaging based on the Hornbeck and Haynes model [J. A. Hornbeck and J. R. Haynes, Phys. Rev. 97, 311 (1955)] is presented which describes the trapping effect on the measured lifetime. This model is fitted to experimental spatially resolved data to extract trapping parameters, particularly trap density and the trap-escape ratio, i.e., the ratio between escape rate of minority carriers from the trap level into the minority band (detrapping) and trap rate from the minority band into the trap level (trapping). An upper bound for the low level injection recombination lifetimes is determined. Lifetime and trapping parameters are compared with dislocation density maps. A strong correlation is found between the total trap density and the crystal defect density.

Excess minority carriers, generated in the substrate of metal oxide semiconductor transistors operating in saturation, are known to present reliability problems in dynamic memory circuits such as random access memories and charge coupled devices. It has been shown that the minority carriers result from light emission associated with the avalanche multiplication region close to the drain. In this paper we report evidence of a new minority carrier injection process which only occurs in p‐n junctions having very low breakdown voltages (≲9 V). The avalanching emitter‐base junctions of bipolar transistors were used as the injection sources and injection efficiencies (defined as the ratio of the minority carrier current to the multiplication current) as high as 5×10−3 were recorded. A model of the injection process based on impact ionization within the neutral regions is proposed. A Monte Carlo simulation of avalanche breakdown is used to demonstrate the feasibility of the model.

When radiative (band to band) lifetimes and nonradiative (multiphonon via flaws) lifetimes become comparable, as is the case for GaAs, the customary diffusion equation for minority carriers under low level injection conditions must be augmented by terms originating from photon transport. Using the generalized van Roosbroeck–Shockley relation between absorption and emission as well as radiative transfer theory, the relevant equations for free carrier transport are derived. Subsequently, it is shown that the influence of the reabsorbed recombination radiation on carrier transport while unimportant at low doping levels becomes important for n‐type GaAs at high doping levels. We also determine the external luminescence flux taking due account of multiple emission and absorption events inside the sample.

A solution of the continuity equations is obtained for the space charge distribution by assuming (1) that deviations from neutrality are small, and (2) that the space charge fields, which are a consequence of the terms containing ▿·E in these equations give rise to pure diffusion and pure ``drift‐wave'' terms with time dependent coefficients. It is, for equal numbers of holes and electrons initially injected, e[(p−p0)−(n−n0)]=−τρ∇ lim E·J[1−exp(−t/τρ)], where τρ equals K/4πσ, the relaxation time, J is the total current density including diffusion, as well as drift, and ∇ lim E means that the divergence does not operate on E (the electric field is held constant). In the differentiation ∂n/∂x and ∂p/∂x are considered to be equal, as are ∂2n/∂x2 and ∂2p/∂x2.Working independently, H. Brooks and W. van Roosbroeck arrived at expressions for both the ambipolar diffusion coefficient and the ``group mobility'' of the drift of a pulse of excess carriers. This theory yields the same results, and, in addition, transi...

Two methods are described for the measurement of lifetime of minority carriers. One depends on pulse injection of carriers in a filament and detection, after a known time, at a collector. The second makes use of the decay of the conductivity modulation caused by minority carriers after injection at a single contact. Both measure the lifetime in a small region rather than the average value over a large part of the sample.

The possibility of backward injection of minority carriers in p‐n junctions is shown. It is predicted that in a forward‐biased p‐n junction where this type of injection occurs, heat energy is pumped out of the junction causing it to cool off. Some conditions which lead to backward injection of minority carriers are described. Theory is presented for a particular p‐n junction model in which this new cooling effect takes place. It is shown that a given dc electrical energy may be used to pump nearly an equal amount of heat energy from one of the junctions to the neighboring ones provided that the junction temperatures are sufficiently close to each other.