Void-Semiconductor GaAs Photonic Crystal Surface-Emitting Lasers by Epitaxial Regrowth and Single-Epitaxy Methods

Monolithic semiconductor lasers including edge-emitting lasers (EELs) and vertical-cavity surface-emitting lasers (VCSELs) fail to realize simultaneous achievement of both high-power high-quality beams due to intrinsic limitations of their resonant cavity. Photonic crystal surface emitting lasers (PCSELs) address these structural limitations through employment of a two-dimensional photonic crystal (PC) cavity that creates feedback at a single wavelength for laterally scalable devices. This function of the PC allows PCSELs to power scale with area while maintaining single-mode emission required for diffraction-limited beams. In this way, PCSELs fulfill an industry demand for high-power high-quality lasing from a single chip. Early PCSELs were fabricated by way of wafer fusion where two wafers, the first containing the active layer and the second containing the PC, are joined together via heat treatment in a liquid phase epitaxy furnace. This technique produces a high density of light absorbing defects at the bonded interface. Modern PCSEL fabrication forgoes wafer bonding in favor of processes that maintain crystalline order throughout the entire structure. This work demonstrates PCSEL fabrication by epitaxial regrowth and single- epitaxy methods to illustrate their respective advantages and engineering challenges. While specific properties of epitaxial regrowth are beneficial for total output power, a single-epitaxy process simplifies fabrication and provides a more scalable and wavelength versatile platform. PCSELs with InGaAs multiple-quantum-well (MQW) active regions are constructed by molecular beam epitaxy (MBE) using both regrowth and single-epitaxy methods. Total output power of epitaxially regrown PCSELs is dramatically improved by implementation of a flip-chip bonding process and a metal- organic chemical vapor deposition (MOCVD) regrowth step. By affecting stable large- area coherent lasing, the fabricated PCSELs described in this work address th