Characterization of liquid phase epitaxial GaAs for blocked-impurity-band far-infrared detectors

Characterization of liquid phase epitaxial GaAs for Blocked-Impurity-Band far-infrared detectors B.L. Cardozo a,b L.A. Reichertz c,b J.W. Beeman b E.E. Haller a,b, ∗ a Department of Materials Science and Engineering, University of California Berkeley, Berkeley, California 94720, USA b Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA c Department of Physics, University of California, Berkeley, California 94720, USA Abstract GaAs Blocked-Impurity-Band (BIB) photoconductor detectors have the potential to become the most sensitive, low noise detectors in the far-infrared below 45.5 cm −1 (220 µm). We have studied the characteristics of liquid phase epitaxial GaAs films relevant to BIB production, including impurity band formation and the in- frared absorption of the active section of the device. Knowledge of the far-infrared absorption spectrum as a function of donor concentration combined with variable temperature Hall effect and resistivity studies leads us to conclude that the optimal concentration for the absorbing layer of a GaAs BIB detector lies between 1 × 10 15 and 6.7 × 10 15 cm −3 . At these concentrations there is significant wavefunction over- lap which in turn leads to absorption beyond the 1s ground to 2p bound excited Preprint submitted to Infrared Physics & Technology 7 April 2004