Recombination Emission in InSb

TLDR: In this article, the emission of phonon-assisted transitions is about 150 times weaker than that of direct transitions; this ratio is consistent with the strength of polar-mode coupling.

Abstract: Optically excited recombination emission has been studied for $n$- and $p$-type single-crystal samples of InSb at 77 and 4.2\ifmmode^\circ\else\textdegree\fi{}K. Emissions associated with band-to-band transitions, transitions with creation of an optical phonon, and transitions involving acceptor impurities have been observed. The band-to-band emission in the pure samples can be attributed to direct transitions, whereas the emission in samples of high donor concentrations clearly shows transitions violating wave-vector conservation. The emission of phonon-assisted transitions is about 150 times weaker than that of direct transitions; this ratio is consistent with the strength of polar-mode coupling. The $n$-type as well as the $p$-type samples show an emission band due to electron transitions from the conduction band to some impurity level at 7.5 meV above the valence band, and the emission is much more prominent in the Zn-doped samples. Germanium-doped $p$-type samples show a weak emission band associated with an acceptor level at 17 meV above the valence band. Samples of large donor concentrations show the effect of band tailing. The main impurity emission increases linearly while the band-to-band emission increased quadratically with the intensity of exciting light. From the shift and splitting of the emission under applied magnetic field, an electron effective mass of ${m}_{e}\ensuremath{\sim}0.018m$ and an electron $g$ factor of $|g|=40 \mathrm{at} 30$ kG are obtained. Electroluminescence has been observed in $p$-type crystals under pulsed electric fields of \ensuremath{\sim}60 V/cm. The observed spectrum appears to be a broadened impurity line. The emission is more than an order of magnitude weaker than optically excited emission corresponding to the same sample conductance.