Long Wavelength Characterization of Internal Quantum Efficiency in LT-GaAs MSM Photodiodes

Abstract

ABSTRACTMetal-Semiconductor-Metal (MSM) photodiodes fabricated from low temperature (LT) grown GaAs by molecular beam epitaxy have been characterized for wavelengths extending out to 1.5μm. External quantum efficiencies on the order of 0.5 % have been measured for subbandgap wavelengths, which translates to internal quantum efficiencies of 2–4 % for the interdigitated electrode structure with lμm finger spacing and width. Although the effective lifetime of the LT-GaAs has been determined to be <1ps, an MSM photodiode response of ∼10ps full width at half maximum was measured by correlation techniques at 820 nm wavelength, and a system limited response of 3GHz was measured at 1.3 μm wavelength. These experimental results will be described in detail.