Photoluminescence mapping and angle-resolved photoluminescence of MBE-grown InGaAs/GaAs RC LED and VCSEL structures

Abstract

In this paper we report a systematic investigation of emission properties of microcavity devices [resonant-cavity light-emitting diodes (RC LEDs) and vertical-cavity surface-emitting lasers (VCSELs)] fabricated from molecular beam epitaxy (MBE)-grown heterostructures. The optimization of such structures requires proper tuning of the wavelength of radiation emitted from the quantum-well active region, the peak reflectivity of Drs and the cavity resonance. We demonstrate results of two techniques used to study InGaAs/GaAs RC LED and VCSEL structures. The first method is spatially resolved photoluminescence, i.e. mapping of the spontaneous emission and the cavity resonance wavelength over the whole epitaxial structure, which allows for precise determination of wavelength tuning of the structure with resonant cavity. On the other hand, it should be borne in mind that the frequency of the cavity resonance depends on the angle of observation. To study this effect we performed angle-resolved emission measurements, which yield information about the directionality of RC LED emission. The results of the study provide a better understanding of the physical processes underlying light generation in microcavity devices. The information provided by both methods is crucial for designing optimum MBE growth processes and for selecting the areas of the wafer from which useful devices can be fabricated. Since the measurements were made at room temperature they are directly applicable to devices.