Development of a GaAs based BIB detector for sub-mm wavelengths

Gallium arsenide is a promising material for large photoconductor arrays to be operated at submm wavelengths, where currently small stressed germanium arrays are used. The smaller binding energy of shallow donors in GaAs compared to Ge results in response at longer wavelengths without having to apply uniaxial stress. Use of n-type GaAs will greatly simplify the production of detector arrays and therefore allow much larger numbers of pixels. We have grown n-doped GaAs epitaxial films and demonstrated high absorption coefficients at wavelengths exceeding 300 μm. Combined with a high purity GaAs layer, a blocked impurity band (BIB) detector can be formed in order to simultaneously achieve efficient absorption and low dark currents. Recent progress in GaAs epitaxy technology allows production of such multilayer devices in wafer size. We are presenting the characterization results of our preliminary GaAs BIB structures.