Comparison of photoresponsive drain conduction and gate leakage in N-channel pseudomorphic HEMT and MESFET under electro-optical stimulations

Abstract

Photoresponsive drain conduction and gate leakage characteristics of n-channel PHEMT and MESFET are comparatively reported as a function of electro-optical stimulation (V(GS), V(DS), P(opt); lambda = 830 nm). Both in PHEMT and MESFET, a strong nonlinearity of drain photoresponse (R) with P(opt) was observed and can be modeled empirically as R = kappa P(opt)(-beta) (kappa(PHEMT) >> kappa(MESFET)) where model parameters kappa and beta accommodate differences in device/epitaxial structures and electrical biases. Gate leakage current was linearly increasing with P(opt) while it was independent of V(DS) in both PHEMT and MESFET, However, I(G) was a strong function of V(GS) in PHEMT while it was almost independent in MESFET due to suppressed modulation of photoresponsive depletion width with heavy channel doping. Photonic gate response (R(pG)), on the other hand, was observed to be constant in MESFET while it was a strong function of electrical bias in PHEMT.