Epitaxy of High-Power Diode Laser Structures

Abstract

Abstract. Excellent semiconductor-material quality is an essential prerequisite for the fabrication of high-power diode lasers and laser bars. This review discusses issues in the epitaxial growth of semiconductor materials and layer sequences that form the basis for diode lasers. First, an overview of the material systems used for diode lasers with emission wavelengths extending from the far-infrared to the blue range of the spectrum is presented. The following sections then concentrate on materials that have, until now, been used for high-power diode lasers: the GaAs-based, and to a lesser extent also the InP-based members of the III-V family (Al, Ga, In)(As, P). Different growth techniques are described, with stress on the two modern methods -Molecular-Beam Epitaxy (MBE) and Metalorganic Vapor-Phase Epitaxy (MOVPE) -that are currently used for the growth of diode-laser structures. An attempt is made to compare the relative strengths and weaknesses of these epitaxial growth techniques.The issues of purity, ordering (observed for example in GaInP), phase separation (occurring for certain compositions of GaInAsP) and p-and n-type doping for the constituent III-V materials found in high-power diode lasers are discussed in detail. The sequential growth of layers of controlled thicknesses, composition and doping profiles to build up the desired heterostructures requires careful optimization of the growth processes, especially at the heterointerfaces. While most of the layers within the heterostructure are lattice-matched to the underlying substrate, the active, light-emitting layer usually consists of one or more strained quantum wells (QWs). The advantages of such strained layers along with the corresponding implications from the growth viewpoint are highlighted. Finally, an overview of the different material combinations used and the state-of-the-art for 600-1060 nm emitting GaAs-based diode lasers is presented.The first reports on semiconductor-diode lasers [1] date back to 1962. Since then these devices have been realized over a wide range of emission wavelengths in a variety of material systems. Since the first demonstration of the semiconductor laser, threshold-current densities have fallen by more than three orders of magnitude, due to various breakthroughs made possible primarily by advancements in crystal-growth technologies. Improvements in Liquid-Phase Epitaxy (LPE) in the early 1970s enabled the realization of the Double Heterostructure (DH) concept and Continuous-Wave (CW) operation of GaAs/AlGaAs lasers, while progress in growth technologies like MolecularBeam Epitaxy (MBE) and Metalorganic Vapor-Phase Epitaxy (MOVPE) were responsible for the development of quantum-well lasers, which are the basis of most high-power diode lasers today. This review describes and compares the different epitaxial growth methods used to fabricate diode lasers in various material systems and examines important growth-related issues such as doping, ordering and homogeneity that are essential for the successful fabrication of ...

Effects of radiation on laser diodes.

“…Addition of Al into the active region causes a degradation of the device performance due to the introduction of centers for nonradiative recombination. 12 A comparison of laser diode materials emitting at 808 nm is shown in Table 1. It should be noted that even though aluminum is detrimental in the active layer, a completely aluminum-free laser diode structure is not desirable.…”

Deep-learning-based visual inspection of facets and p-sides for efficient quality control of diode lasers

“…Starting with the substrate of the wafer, the vertical structure of the diode laser is grown using, for example, metal-organic chemical vapor phase epitaxy. 1 After the epitaxy is finished, the lateral and longitudinal layout of the diode lasers is created by a combination of photo-and electron-beam lithography, wet and plasma etching, and various types of metallic and dielectric deposition methods. The finished wafer is then cleaved into diode laser bars to process the facets.…”

Use of a Small Lattice Mis-Matched Metamorphic Substrate to Extend the Wavelength Range of a Broadband, Polarization Insensitive Semiconductor Optical Amplifier

“…This limits the long wavelength range accessible with tensile strained InGaAs QWs grown on InP such that amplification of signals in the long wavelength part of the Lband window is not accessible. Second, growing tensile strained materials on InP puts the compositions deep within the spinodal decomposition regime where the material will exhibit phase separation [1] [2].…”