Avalanche formation and high-intensity infrared transmission limit in InAs, InSb, andHg1−xCdxTe

High-intensity infrared transmission in $n$-InAs, InSb, and ${\mathrm{Hg}}_{1-x}{\mathrm{Cd}}_x\mathrm{Te}$ ($x=0.23\mathrm{}$) has been examined by subjecting samples of these narrow-gap semiconductors to laser radiation of nanosecond duration at 10.6 μm. In each case a distinct high-intensity transmission limit was observed, beyond which further increases in incident intensity caused a rapid and large decrease in the transmission coefficient. Such "self-enhanced opacity" has been observed to occur on subnanosecond time scale. We have suggested an explanation by considering a model in which hot-electron generation by intraband absorption leads to an avalanche of excess carriers with a large cross section for intervalence band absorption for holes at 10.6 μm. Our results are of relevance to current work on laser-excited plasmas and their device applications in narrow-gap semiconductors.