Spontaneous and Stimulated Light Emission Due to Radiative Recombination in Forward Biased Lead Telluride P-n Junctions

摘要

The results of a number of experiments on the light emission and electrical characteristics of lead telluride p-n junction diodes have been presented. The capacitance-voltage data indicate that the vapor diffusion of an n-type layer into p-type bulk material produced an abrupt junction. At low current levels and temperatures (4.2K to 20.4K), the current voltage data exhibit a temperature independent exponential variation of current with junction voltage. The current-voltage data, together with the total intensity data as a function of diode current, indicate that photon-assisted tunneling is the dominant injection mechanism at low current levels. As the current level is increased, the injection mechanism changes from photon-assisted tunneling to thermionic emission. The spontaneous emission of light in the thermionic injection region is apparently influenced by impurity trapping levels in the band-gap. Stimulated light emission occurs at high injection levels in those diodes where a reflecting cavity is formed by cleaving the ends of the crystal. The image-scan and far-field diffraction data indicate that the stimulated electromagnetic modes are confined to within approximately a diffusion length of the junction. The data indicate that the mode confinement is due to the optical gain in the diode cavity, a gain which obtains in the region where a population inversion exists. Therefore, both the gain and the mode profiles are diffusion controlled. (Author)