Intervalence band absorption in bulk InSb lasers

Four-band Kane theory with the effects of remote bands included via perturbation theory has been used to predict the gain spectra in the active region of bulk InSb under injection. The effect of intervalence band absorption (IVA) between light and heavy hole bands has been included by calculation from first principles and is found to increase in significance with increasing temperature. Comparison with experimental absorption spectra for doped samples shows good agreement indicating the model´s validity. The authors show that to achieve room temperature operation, carrier densities of the order of 5×10¹⁸ cm^-3 are required to overcome IVA. Such carrier densities are unlikely to be attainable in bulk devices owing to the large Auger coefficients associated with InSb. Consequently, uncooled laser operation in a device relying on purely bulk InSb properties does not seem practical