Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract A new GaAs photodetector with high sensitivity in the whole 0.8–1.4μm wavelength range has been fabricated from totally depleted GaAs doping superlattices grown by molecular beam epitaxy. Photoexcited electrons and holes are separated in real space by the space-charge field of the doping superlattice immediately after excitation, yielding a high quantum efficiency of this device. Because of the complete depletion, the doping superlattice behaves like a highly resistive material, which allows application of high electric field along the layers via selectiven + — andp + -electrodes. The sensitivity of this device at 1.3 μm reaches more than 90% of the original band edge response at 0.85 μm, and the external quantum efficiency amounts to 65% at 0.85 μm. This excellent photoresponse at longer wavelengths arises from an extremely high electric field composed of the intrinsic space charge field and applied external field, and from the existence of pronounced tail states in the forbidden gap region of the superlattice.
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