Reliable and rapid test structure fabrication and characterisation techniques are required in a high volume production environment to assess material quality and suitability for end product applications. As materials and growth techniques continue to evolve an increasing number of methods are required to investigate the relationship between layer design, material growth and device performance. Reliability, speed and the cost-effectiveness of these techniques are key considerations.
Simple production techniques exist to examine the emission spectrum of VCSEL material in the direction of the lasing cavity. This work investigates an ultra-fast method to obtain detail of the active region emission wavelength independent of the distributed Bragg mirror stack by examining the electronic structure of the material.
Rather than directly observing light emission perpendicular to the lasing direction, which can result in a convolution of the emission and absorption spectrum, a technique that measures a photo-voltage spectrum by illuminating the edge of the wafer (perpendicular to the lasing direction) is employed. Illumination in this configuration can also allow information regarding the strain of the quantum wells to be determined. This technique requires very few fabrication steps and is highly cost effective. Rapid techniques to fabricate VCSEL test structures for comparison between material characteristics and device performance are also investigated.
Lewis Kastein, Peter M. Smowton, and Graham Clarke, "Rapid fabrication and characterisation techniques for VCSELs (Conference Presentation)," Proc. SPIE 10122, Vertical-Cavity Surface-Emitting Lasers XXI, 101220D (Presented at SPIE OPTO: February 02, 2017; Published: 20 April 2017); https://doi.org/10.1117/12.2255947.5397967401001.
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