CHARACTERIZATION OF HIGH-PURITY GAAS FAR-INFRARED PHOTOCONDUCTORS

In this paper we report the results of an extensive study on the far-i nfrared photoconductivity of high purity n-type GaAs. The crystal, whi ch was grown at Max-Plank-Institute for Solid State Physics using liqu id-phase epitaxy, exhibited the fine structures of the excited state t ransitions of the residual shallow level impurities. The major peak in the spectral response belongs to the 1s-2p transition, with its respo nsivity about thirty five times higher than the continuum. At 3.4K det ector temperature, 625 mV bias, and 100 Hz chopping frequency the dete ctor responsivity at 35.4 cm(-1) (279 mu m) was measured to be 0.017 A /W. Under these same conditions, the NEP was 5.9x10(-14) W/root Hz. Th e (DC) dark current at 25 mV bias was 5.6x10(-14) A.