A comparison of optoelectronic properties of lattice-matched and strained quantum-well and quantum-wire structures

The k/spl middot/p formalism is used to study the absorption spectra, material and differential gain in quantum wires as a function of orientation, built-in strain, and wire dimensions. The results for material and differential gain are compared with those for an optimized quantum-well structure. We find that for quantum wires at 300 K, the gain becomes positive at a carrier density of 1.27/spl middot/10/sup 18/ cm/sup /spl minus/3/, while in quantum wells this density is calculated to be 1.82/spl middot/10/sup 18/ cm/sup /spl minus/3/. Incorporating tensile strain in the wires reduces the transparency carrier concentration to 0.96/spl middot/10/sup 18/ cm/sup /spl minus/3/ while compressive strain allows one to obtain positive gain for densities greater than 1.08/spl middot/10/sup 18/ cm/sup /spl minus/3/. Orienting the wire along the /spl lsqb/111/spl rsqb/ direction reduces the transparency carrier density to 0.60/spl middot/10/sup 18/ cm/sup /spl minus/3/. The differential gain in quantum-well structures for injections near the threshold is on the order of 10/sup /spl minus/14/ cm/sup /spl minus/4/, while for 50 /spl Aring//spl middot/100-/spl Aring/ quantum wires the differential gain near the threshold is found to be on the order of 10/sup /spl minus/13/ cm/sup /spl minus/4/. The differential gain in wires whose wire axis is parallel to the /spl lsqb/111/spl rsqb/ direction has also been found to be on the order of 10/sup /spl minus/13/ cm/sup /spl minus/4/ for carrier injections close to the threshold.<
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