LASER ACTION AND PHOTOLUMINESCENCE IN AN INDIUM-DOPED N-TYPE HG1-XCDXTE (X=0.375) LAYER GROWN BY LIQUID-PHASE EPITAXY

Photoluminescence, carrier lifetime, and laser oscillation in an indiu m-doped n-type Hg1-xCdxTe (x = 0.375) layer grown by liquid phase epit axy on CdZnTe were studied. A single-line photoluminescence spectrum w as observed up to room temperature. The temperature-dependence of the photoluminescence peak energy and linewidth agrees with a model of ban d-to-band transitions obeying the k-conservation rule. The carrier lif etime derived from the observed photoluminescence intensity agrees wit h the observed photodecay lifetime in the temperature range 12-200 K. Laser action was observed in the temperature range 12-90 K at lambda = 3.6 mum. The laser threshold power increased exponentially with tempe rature, with a characteristic temperature of 17.5 K. The calculated eq uivalent threshold current density was found to closely follow the obs erved one, indicating a maximum threshold gain of 150 cm-1. The calcul ation shows that at low temperature the threshold power is determined by radiative recombination, while above 50 K Auger recombination becom es dominant. The high value of the threshold gain is attributed to the gain guiding mechanism governing this laser device operation. The obs erved differential quantum efficiency decreased from 15% at 12 K to 4% at 90 K. A possible mechanism giving rise to this decrease in the eff iciency is discussed. The spectrum of the laser with a 3-mum-thick act ive layer exhibited at high pumping power up to three lines, which wer e attributed to index guided transverse modes. The 9-mum-thick active layer device exhibited a quasisingle mode spectrum most probably due t o gain guiding in both the lateral and the transversal directions.