ROOM-TEMPERATURE BAND-EDGE PHOTOLUMINESCENCE FROM CADMIUM TELLURIDE

Room-temperature photoluminescence (PL) spectroscopy of II-VI semiconductor alloys has been proposed as a useful tool for determination of spatial variations in alloy concentration and impurity concentration. However, the nature of the PL recombination can affect the emission peak energy, as well as line shape. These effects in the band-edge emission of the compound II-VI semiconductor CdTe are reported here. PL measurements at 300 K were recorded from (1) highly doped n-type CdTe films grown by molecular-beam epitaxy, (2) undoped high-resistivity (rho similar to 10(8)-10(9) Omega cm) bulk CdTe, and (3) as-grown nominally p-type (rho similar to 10(4)-10(5) Omega cm) bulk CdTe. The dependence of PL emission intensity and line shape over a range of excitation from 0.003-70 W/cm(2) was studied. As the excitation power density was increased, a redshift in PL peak position was observed from all samples. PL peak position, intensity, and line-shape analysis show the highly excitonic nature of the radiative recombination in these materials, even though the free-exciton binding energy in CdTe is about 1/3 of kT at 300 K. In addition, the PL peak position can be more than 7 meV higher from n-type CdTe as compared to undoped CdTe.