Exciton Absorption and Emission in InP

Sharp peaks due to exciton formation have been observed in the intrinsic optical-absorption-coefficient data for undoped indium phosphide at 6, 20, and 77°K. At 298°K, the absorption data do not show a peak, because of thermal broadening. Low-temperature photoluminescence data obtained on the same InP used for absorption data exhibited an exciton emission peak at the same energy as the absorption peak and confirm the earlier identification of the emission line due to Turner and Pettit. At 6 and 77°K, the exciton peak energies are 1.416 and 1.409 eV, respectively. From the absorption data, the exciton binding energy at both temperatures is 0.0040 eV. The temperature dependence of the gap in the linear region above 100°K is -2.9×10-4eV/°K, in sharp disagreement with the earlier value of Oswald. © 1964 The American Physical Society.