Bismuth-doped Pb1-xSnxTe diode lasers with low-threshold currents

Diode lasers have been fabricated from Bi-doped Pb1-xSnxTe with0.24 leq x leq 0.27, which have threshold current densities as low as 1400 A.cm^-2at 77°K and 71 A.cm^-2at 12°K, whereas diodes fabricated from undoped Pb1-xSnxTe> in this composition range did not exhibit laser action for current densities up to 30 000 A.cm^-2at 77°K and had threshold current densities greater than 200 A.cm^-2at 12°K. Bi doping also results in a reduction in the annealing times required to form suitablep-njunctions from several weeks to a few days. These effects can be tentatively related to an increased electron concentration in then-type layer due to the addition of Bi, a donor impurity. A curve ofEgversusxfor0 leq x leq 0.4, which agrees with predictions, is presented.