Molecular Beam Epitaxial Growth and Characterization of Novel VCSELs at 1.55 micron

The vertical-cavity-surface-emitting laser(VCSEL) which operate at 1.55 or 1.3 um has been recognized as a key device in optical interconnection systems and parallel optical processing. However, the realization of these long-wavelength VCSELs with a low threshold current has long been delayed due to the absence of a highly-reflective distributed Bragg reflector(DBR). A DBR reflectivity exceeding 99.9% is required to apply a quantum well active layer with which a sufficiently low threshold current density is expected. Due to small index differences between InP and InGaAsP materials, most of promising work on these VCSELs employed hybrid approach( wafer fusion). The reliability, reproducibility, and yield/cost is a concern. Although there are a few monolithical approaches, no promising result has been achieved. ELI proposes a novel monolithical approach to fabricate DBRs and hence VCSELs using MBE. The proposed approach will take advantage of ( 1 )large index difference, hence requiring less than 20 pairs to achieve 99.9% reflectivity; (2) lattice matched direct growth on InP substrate; (3) with selective oxidation it is possible to obtain 99.9% reflectivity with only 5 pair of the quarter-wave mirror stacks. In phase I, DBR will be demonstrated, and VCSELs will be realized in phase II. VCSELs, due to the advantage of wafer-scale testing and ease of fabrication of laser arrays, have applications in optical interconnection systems and parallel optical processing including optical data links, printers, and displays. 1.5 um VCSELs are particularly ithportant in the optical fiber communications, including wavelength division multiplexing.