Calculation of the minorityhyphen;carrier confinement properties of IIIhyphen;V semiconductor heterojunctions (applied to transmissionhyphen;mode photocathodes)

摘要

For electrohyphen;optical device applications, the principal properties desired of a heterojunctions are minorityhyphen;carrier confinement and a change in optical parameters. It is shown that for IIIhyphen;V materials with heavily doped junctions the minorityhyphen;carrier confinement properties may be approximately calculated from the materials parameters by using a simple relationship. The critical parameters are shown to be the minorityhyphen;carrier diffusion length, the device operating temperature, and the rate at which the band gap of a materials system varies with lattice constant. The effective interfacial recombination velocity into the highhyphen;bandhyphen;gap side of a heterojunction is calculated from these parameters, and is in turn used to calculate the properties of transmissionhyphen;mode IIIhyphen;V photocathode devices. Some materials systems such as GaAssngbnd;AlGaAs and InPsngbnd;InGaAsP demonstrate nearhyphen;ideal performance as photocathodes, while other commonly used materials systems such as GaAssngbnd;GaAsP are shown to be fundamentally incapable of good performance. A difference in electrical properties is demonstrated between liquidhyphen;phasehyphen;epitaxially grown heterojunctions and vaporhyphen;phasehyphen;epitaxially grown heterojunctions.