Extraordinary optoconductance in InSb-In hybrid structures

Previously reported extraordinary optoconductance (EOC)\footnote{ K.A. Wieland \textit{et al.}, Applied Physics Letters, submitted.} in degenerate Si-doped $(n\sim 1 \times 10^{18}$ cm$^{-3})$ GaAs-In metal-semiconductor hybrid structures (MSHs) is compared to new experimental results on intrinsic Te-doped $(n\sim4 \times 10^{14}$cm$^{-3})$ InSb-In MSHs. Using a shunted van der Pauw plate, DC and AC voltage measurements of InSb MSHs were acquired. The sample was illuminated with a focused Ar ion laser and studied as a function of wavelength $(457-526$nm$)$, bias current $(\pm100$mA$)$, lateral position (transverse to the beam), and at 300K and 10K. Whereas the optimal room temperature position sensitivity in the case of GaAs is 137 mV/mm for 100mW of 488.0 nm illumination, the corresponding sensitivity of InSb is found to be 1.2 mV/mm for 10 mW of 514.5 nm illumination. The magnitude of the InSb result is surprisingly large given the relative values of band gaps, mobility, carrier concentration, and laser illumination.\footnote{O. Madelung, editor, Data in Science and Technology: Semiconductors - Group IV Elements and III-V Compounds (Springer, New York, 1991).} The origin of this large position sensitive photovoltage will be discussed.