ROOM-TEMPERATURE BAND-EDGE PHOTOLUMINESCENCE FROM CADMIUM TELLURIDE

Room-temperature photoluminescence (PL) spectroscopy of II-VI semicond uctor alloys has been proposed as a useful tool for determination of s patial variations in alloy concentration and impurity concentration. H owever, the nature of the PL recombination can affect the emission pea k energy, as well as line shape. These effects in the band-edge emissi on of the compound II-VI semiconductor CdTe are reported here. PL meas urements at 300 K were recorded from (1) highly doped n-type CdTe film s grown by molecular-beam epitaxy, (2) undoped high-resistivity (rho s imilar 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 fr om 0.003-70 W/cm(2) was studied. As the excitation power density was i ncreased, 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, e ven 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 hig her from n-type CdTe as compared to undoped CdTe.