Properties of diffused PbSnSe homojunction diode lasers

The properties of diffused PbSnSe homojunction diode lasers based on the confinement of injected carriers and of light in the fundamental transverse laser mode are investigated both theoretically and experimentally. The electrostatic potential profile near the graded junction is evaluated for the strongly forward biased case. Resulting injection and gain profiles are narrow and their widths increase with temperature. Free carrier dispersion leads to an optical confinement. From the threshold condition for the TEM
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mode, the threshold current density is obtained, assuming a minority carrier lifetime of 2 ns. PbSnSe diode lasers were fabricated by diffusion of cadmium under different conditions. Experimental laser properties for different junction gradings are discussed in terms of the model. Threshold currents and output powers as a function of temperature, as well as maximum operating temperature and mode behavior, are consistent with the theoretical expectations.