Development of n-type Te-doped GaSb substrates with low carrier concentration for FPA applications

Unlike the production of highly resistive, semi-insulating GaAs substrates, production of GaSb substrates with low absorption coefficients is less mature due to the problems associated with the reduction of the residual native acceptors. Undoped GaSb is p-type with the residual acceptor concentration of about 1e-17 cm-3 due to the gallium vacancies with net excess gallium atoms in antimony lattice sites. One of the known pathways to achieve optical transparency in a broad IR spectral range is to counter-dope GaSb with Te to reduce the residual hole carrier concentration. In this work, we report net p-doping concentration as low as ~3e15 cm-3. Application of non-destructive FTIR spectroscopy mapping of the substrate’s optical transparency for correlation to the carrier concentration distribution across GaSb wafers shall be discussed. By cross-correlating the data between the Hall and FTIR methods, we are able to establish empirical relations between the absorption coefficient of GaSb in the IR spectral range and the material’s carrier concentration. We demonstrate a good control over the lateral distribution of the carrier concentration in 4” GaSb n-type wafers doped with Te to 5e16 cm-3 with high optical transparency in the broad IR spectral range.