Optical and photoelectric study of mirror facets in degraded high power AlGaAs 808 nm laser diodes

Abstract

Growth of high-quality GaAs/AlAs Bragg mirrors on patterned InP-based quantum well mesa structuresMirror facets of broad area AlGaAs SQW 808 nm lasers with fast degradation of the output power have been investigated by photoluminescence microscopy ͑PLM͒, electroluminescence microscopy, and micro-photocurrent spectroscopy techniques. Over 2000 images of the photoluminescent light emitted from the facets of approximately 20 degraded laser bars have been made. Repeating patterns associated with the degradation have been noted and classified. Degraded lasers have dark lines on the mirror facet surface which are inclined from the epitaxial plane by 55°. Pairs of such lines often form V-shaped patterns. The orientation of the observed features suggest they are planar or line defects lying the the ͕111͖ crystallographic planes. The defects demonstrate a reduction in the lifetime of nonequilibrium electron-hole pairs and increased density of states in the forbidden gap of the active region of the laser structure, and are directly related to laser failure. Observations of the evolution in size and contrast of PLM patterns with ageing suggest the defects were initially created in the active region side of the laser structures during crystal growth or during the mounting procedure, and later propagate in the ͕111͖ planes, stimulated by the lasing action. We interpret the V formation to be a way to relax a compressive strain in the epitaxial plane. A dislocation on the ͕111͖ planes could actually translate the portion of the crystal bounded by the V upwards ͑away from the mounting of the crystal͒, in response to compressive strain.

Atomic force microscopy based room temperature photocurrent‐spectroscopy of single subsurface InAs quantum dots

“…Photocurrent spectroscopy applications range from investigations of interband [3], intraband [4], intersubband [5,6] and intrasubband [7] transitions in heterostructures and quantum dot systems [8][9][10] to investigations of organic films [11], organic devices [12] and the analysis of dielectric materials [13]. Some efforts have been made to increase the spatial resolution of photocurrent measurements by either using shadow masks to define the illuminated sample areas [14] or by using a carefully focused and collimated beam of light [15]. One can also find some scanning near field optical microscopy (SNOM) approaches to increase the spatial resolution into the nmregime [16].…”

Operation and Catastrophic Optical Degradation of II-VI Laser Diodes at Output Powers larger than 1 W

“…3 2 Þ). Such ''V"-shaped defects are not solely a phenomenon of II-VI lasers, they are also known from AlGaAs laser diodes [6]. While these structures exhibit ''V"-shaped defects starting only from the active region, such defect formation can be observed on the whole structure of ZnSe-based LDs [7].…”

A Spectroscopically Resolved Photo- and Electroluminescence Microscopy Technique for the Study of High-Power and High-Brightness Laser Diodes

“…Indeed, our current experimental setup can also be used to perform -PL measurements if a higher spectral resolution is required. The excitation spot is easily positioned on the site of interest on the sample by using the standard PLM imaging system [24].…”

“…A more-detailed description of this multifunction instrument can be found elsewhere [22], [24], [28], [31]. The new spectroscopically resolved techniques bring together PLM imaging and PL spectroscopy, resulting in, for the first time, a high-quality imaging technique that is quantitatively calibrated and both spectrally and spatially resolved.…”

“…Microphotoluminescence ( -PL) has been used extensively to measure and study packaging-induced strain [20], [23] and PL microscopy (PLM) has often been used for observing and identifying extended defects [24]- [26]. Photocurrent (PC) spectroscopy [21], [23], [27], micro-Raman [21], [23], and electroluminescence (EL) studies combined with a fast Fourier transform (FFT) analysis [28]- [30] have also been used to study the influences of strain and defects.…”