Spatially Variable Drift Mobility Model for Hg1−xCdxTe Diodes. II. Application to Device Simulation

Abstract

A spatially variable drift mobility model for Hg,-$d,Te with x x 0.2, outlined in a previous paper, is applied to infrared photodiodes. For this purpose the mobility program was self-consistently incorporated into the 2D device simulator TOSCA. Zero voltage mobility profiles of electrons and heavy holes are obtained restricting the scattering mechanisms to polar optical phonon and ionized impurity scattering for clearness. Besides the doping profile and the dominating scattering processes, the local mobility is determined by degeneracy and screening effects. Forward biased, heavily doped junctions exhibit a remarkable change of the mobility profile. The averaged mobility increases with rising positive voltage, which results in steeper I-U curves. The reverse biased mobility profile is only little affected, but reflects the increasing depletion by a broadening mobility well. Ein ortsabhangiges Model1 der Driftbeweglichkeit in Hg, -,Cd,Te rnit x = 0,2, das fruher entwickelt wurde, wird auf Infrarot-Photodioden angewendet. D a m wurde das Beweglichkeitsprogramm selbstkonsistent in den 2D-Bauelemente-Simulator TOSCA eingebaut. Man erhdt Beweglichkeitsprofile der Elektronen und schweren Locher im Gleichgewicht, wobei zur Deutlichkeit nur die Streuung an polar-optischen Phononen und ionisierten Storstellen berucksichtigt wurde. Neben dem Dotierungsprofil und den dominanten Streuprozessen wird die lokale Beweglichkeit ,)on Entartungs-und Abschirmungseffekten bestimmt. Stark dotierte und positiv vorgespannte Ubergange zeigen eine betrachtliche Veranderung des Beweglichkeitsprofils. Die mittlere Beweglichkeit wachst mit steigender positiver Spannung, was zu steileren I-U-Kurven fiihrt. Im Sperrfall wird das Beweglichkeitsprofil nur leicht verandert, es spiegelt jedoch direkt die wachsende Verarmung durch ein breiter werdendes Beweglichkeitsminimum wieder.

Unified bulk mobility model for low- and high-field transport in silicon

“…͑5͒ the electron density is indeed given by the usual Fermi integral (nϭN c F 1/2 ) and not by its nonparabolic modification (nϭN c J 1/2 ), discussed, e.g., in Ref. 16. This can be easily proven evaluating the zeroth moment of f (0) (k).…”

“…One finds that the ratio is given by n,ac Kohler ϭ(9/32) n,ac RTA which is the known failure of the Kohler method in first order (⌽(k)ϭa 0 k z ). 16 For the goal of this work-the derivation of a closedform expression that combines high-and low-field mobility-the RTA has still another drawback: even if approximate RTs would be used, the reciprocal summation rule to obtain the total RT finally would prevent an analytical integration.…”