Investigations of vertical cavity surface emitting lasers (VCSEL) resonant cavities by photoreflectance spectroscopy

Photomodulated reflectance spectra of vertical cavity surface emitting laser (VCSEL) wafers have been measured between 9 K and 300 K. Structures used are grown in the AlGaAs based system, and are top surface emitting ones centered near 800 nm, with a lambda cavity, similar to those currently found in literature. One consists of a n⁺ DBR (Distributed Bragg Reflector) mirror and the cavity, the other is a full one: n⁺ DBR mirror, cavity and p⁺ top DBR mirror. For both structures photoreflectance measurements between 300 K and 9 K give interesting information on quantum wells and static electric field in the cavity. In this paper we discuss about the potentialities of this technique for the calibration of VCSEL growth, and its unique non invasive capability to determine quantum well/cavity alignment at room temperature comparing photoreflectance and reflectivity measurements, for vertical cavity devices.