A. L. McWhorter

Electromagnetic theory of the semi-conductor junction laser

Abstract A review is given of the electromagnetic mode properties of the present semiconductor junction lasers. Previous treatments are simplified, and also generalized, by the basic approximation of representing the active region as a lumped negative sheet conductance and sheet susceptance. A lower limit for the threshold current density is given in terms of the bulk absorption coefficient and surface reflectivity. Transitions between impurity levels, or impurity bands, are briefly discussed.

Solid-State Maser Amplifier

The operation of a solid-state maser amplifier at 2800 Mc/sec is described. A dual-frequency cavity containing paramagnetic potassium chromicyanide in an isomorphous cobalt diluent is used at 1.25°K. The experimental observations of the maser both as an amplifier and as an oscillator are compared with theory.

Comparison of a rate-equation model with experiment for the resonant tunneling diode in the scattering-dominated regime

A quasistatic rate-equation model for the resonant tunneling diode (RTD) is presented. In this model, the RTD is divided into three regions, each assumed in quasithermal equilibrium. The electron transfer between states in adjacent regions, assumed to be by elastic tunneling, is then proportional to the probability that the initial state is occupied and the final state is empty. Using this approach, we derive a small-signal equivalent circuit. The model parameters may be either calculated or measured in a fairly straightforward manner, as is demonstrated for an In0.53Ga0.47As/AlAs RTD. We find that the dc characteristic and ac behavior up to 4 GHz are modeled well; we also find that the measured and calculated parameters agree to approximately a factor of 2 except in the vicinity of the current valley. We show that this approach is accurate enough to provide insight into the operation of the device, yields results that are simple enough to be suitable for ac circuit simulation, and should be valid as long...

CURRENT RUNAWAY AND AVALANCHE EFFECTS IN n—CdTe

In addition to Gunn oscillations, n—CdTe exhibits a current runaway which is accompanied by light‐emitting filaments reaching from contact to contact. The results of diagnostic experiments suggest a current‐density controlled differential negative resistivity caused by a bulk avalanche of hole‐electron pairs. The avalanche is probably initiated by high‐field Gunn domains, but the mechanism that sustains the runaway is not understood.

Acoustic plasma waves in semimetals

The acoustic plasma wave suffers severe landau damping for equal-temperature carriers obeying Boltzmann statistics, but can be relatively weakly landau damped in semimetals if in the propagation direction the Fermi velocities and masses of the two carriers are very unequal. Only the carriers with the smaller Fermi velocity are important in producing collision damping since the other carriers store no appreciable momentum. Some results for many-valley semimetals like bismuth are given, together with a discussion of the problem of exciting and detecting this essentially neutral and longitudinal wave. Experiments undertaken to detect the acoustic plasma waveb y transmission through thin wafers of bismuth at 10 Gc/sec have been unsuccessful thus far, but have revealed the existence of a higher velocity wave of weak amplitude that has not yet been identified. A discussion is also given of some magnetic quantum effectsth at should be associated with the acoustic wave.

Compound cryosars for low-temperature computer memories☆

Abstract The compound cryosar, which operates at liquid-helium temperature, consists of two regions of compensated germanium, one more heavily doped than the other, in series between two ohmic contacts. When the more lightly doped region is broken down by impact ionization of the impurities, the impurity conductance of the more heavily doped region limits the current. This current limiting, in addition to the negative resistance of the breakdown, permits one to use a matrix array of compound cryosars in a coincident-voltage memory. If desired, the impact ionization breakdown of the more heavily doped region may be used for a non-destructive readout. High-density arrays of compound cryosars can be operated in a high-speed (10–100 Mc/s) computer memory, with a power dissipation for 200,000 elements of less than 0·25 W.