Conduction Band Minima in AlAs and AlSb

The photoresponse of surface barrier rectifiers made by evaporating a metal such as gold or platinum on a cleaved surface of AlAs and AlSb has been measured in the front wall configuration. The photoresponse of such units for hv > E_g, where E_g is the energy gap, will be proportional to the absorption coefficient as long as the optical attenuation length is large compared to both the width of the space-charge region and the minority carrier diffusion length. The analysis is essentially the same as that for p-n junctions with the exception that the barrier is at the surface and hence more sensitive to photons of high absorption coefficient. Photoinjection of carriers from the metal into the semiconductor for photon energies where hv < E_g can also be observed