EBIC microscopy of double‐heterostructure laser materials and devices

Abstract

The electron beam induced current (EBIC) mode of the scanning electron microscope (SEM) has been used to characterize double heterostructure laser materials and devices in GaAs/Gal-,Al,As. Scanning the electron probe across the cleaved face of the laser structure shows that displacement of the p n junction with respect to the heterojunctions is not uncommon with displacements -1 pm occurring. Concurrent measurement of the minority carrier diffusion length gives very short lengths of 0.3-0.4 pm, differing from those in much thicker layers. Scanning the electron probe in the contact plane indicates clearly that long-lived lasers exhibit marked heterogeneity during degradation. Considerable complexity and variation is recorded depending upon the fabrication details and degradation conditions adopted. I N T R O D U C T I O NThe fabrication, operation and degradation of GaAs/Gal-,Al,As double heterostructure (DH) lasers continue to attract world-wide interest. Despite this, due mainly to the inherent complexity of the four layer device, there has been surprisingly little metallurgical and microscopical examination of the lasers. We report here how the electron beam induced current (EBIC) mode of the SEM can be used to provide information on (a) p-n junction displacement in fabrication, (b) minority carrier diffusion lengths for modelling of device operation, and (c) heterogeneity and complexity in the degradation of long-lived lasers.