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The authors propose simple, analytic approximations that describe properties of semiconductors with nonparabolic energy bands. The approach is based on the two-level kp model of the semiconductor statistics which includes effects of band nonparabolicity and carrier degeneracy. The new expressions are in the form of a correction to the classical, Boltzmann approximation of the semiconductor statistics and do not introduce any new adjustable parameters. These relations can be applied to both narrow- and wide-bandgap nonparabolic semiconductors. The authors calculate the low-frequency capacitance of a nonparabolic MIS structure and compare the results with an accurate numerical model and experimental measurements of a HgCdTe capacitor. The solution includes the contributions of both types of carriers and the effect of impurity freezeout. The new approximations should be useful for characterization and modeling of semiconductor devices with nonparabolic energy bands. >

The contribution of the graded region of implanted p-n junctions is analyzed using an exponential profile. Though previously neglected, it was recently shown that this contribution to the saturation current of HgCdTe diodes is significant. Assuming a dominant Auger recombination, an analytical solution to the continuity equation is obtained. An expression for the current generation by the graded region is presented for both ohmic and reflecting boundary conditions. A revised condition for a wide region is derived. When the region is narrow, the current differs drastically from that of the zero-gradient case. The effects of the junction depth and the substrate and surface concentrations on the current are investigated. It is shown that the reverse current does not saturate.

Infrared detectors were implemented on InAs self-assembled quantum dots fabricated using Stranski–Krastanov growth mode on InAlAs matrix, lattice matched to InP (0 0 1) substrates. These dots grow with a shape of small elongated boxes, with their long axis along the [ 1 1 0] direction, and with a high concentration of 7×10 10 cm −2 . Photoconductive measurements were performed in all three polarizations. Rich spectra in the range of 50–500 meV, with different polarization selection rules were observed. The bias dependence of peak intensity of the intraband transitions serves as an additional tool to identify their origin. Some of the peaks, which increase linearly with bias, are attributed to bound-to-continuum transitions. Others, which appear only at larger biases, and increase superlinearly, are due to bound-to-bound transitions. The magnitude of detector responsivity at normal-incidence is similar to that obtained for polarization normal to the layers, and is comparable to that achieved in QWIPs. BLIP conditions prevail at 77 K for integral photocurrent response at F#1. The effect of unintentional doping is discussed. It is shown that this doping can be destructive for detector operation unless the density of dots is large.

Heat treatment at 70 °C of low carrier concentration p‐type HgCdTe samples (p0=8×1014 cm−3) generates an inverted surface layer. A two day anneal process below 95 °C did not affect the Hall coefficient, whereas an almost complete recovery was obtained by annealing at 120 °C. While bulk electron mobility, obtained from PEM data, remained high (about 9×104 cm2/V s at 77 K), surface mobility is lower by more than an order of magnitude. Surface recombination velocity indicates a continuous improvement with increased temperature, and the activation energy remains equal to the vacancies energy level. The proposed mechanism is that of positive charges in the sulfide migrating towards the interface and generating an image inversion layer.

Anodic oxide passivation of p-type HgCdTe generates an inversion layer. Extremely high Hall mobility data for electrons in this layer indicated the presence of a two-dimensional electron gas. This is verified by use of the Shubnikov-de Haas effect from 1.45-4.15K. Data is extracted utilizing a numerical second derivative of DC measurement. Three sub-bands are detected. Their relative occupancies are in excellent agreement with theory and with experimental results obtained on anodic oxide as accumulation layers of n-type HgCdTe. The effective mass derived is comparable to expected.