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

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