Study of band gap narrowing effect in n-GaAs for the application of far-infrared detection

The band gap shrinkage DeltaE(g) of n-GaAs in relation with the doping concentration (N) is still controversial in various theories and experiments. Most of the experimental results of DeltaE(g) from photoluminescence have already been questioned to have an overestimation by a few tens of meV. We have carried out detailed temperature-dependent transmission experiments on an n-GaAs homojunction far-infrared (FIR) detector structure. By calculating the transmission spectra taking into account the band tail effect, we obtained a 1/3 power rule of DeltaE(g) in n-GaAs by DeltaE(g) = -3.60 x 10(-8) (eVcm) N-1/3. Our results support Harmon et al.'s experimental DeltaE(g) results from the electrical measurements of up product in n-GaAs (Appl. Phys. Lett. 64 (1994) 502). The yielded DeltaE(g) is employed to calculate the cut-off wavelength lambda(c) and dark current of n-GaAs homojunction FIR detectors to investigate the potential application. We find that n-GaAs is more suitable for a long lambda(c) detector design, and has a similar dark current behavior with that of Si and p-GaAs homojunction FIR detectors. (C) 2002 Elsevier Science B.V. All rights reserved.