57 MOVPE Growth of AlGaAs/GaInP Diode Lasers 57 Journal of ELECTRONIC MATERIALS, Vol. 29, No. 1, 2000 (Received May 10, 1999; accepted June 11, 1999) Special Issue Paper MOVPE Growth of AlGaAs/GaInP Diode Lasers INTRODUCTION High power diode lasers operating in the wave- length range 730–1060 nm are of significant interest for applications like pumping fiber amplifiers and solid-state lasers, for soldering, material processing or for applications in medicine, spectroscopy and metrology. In recent years Al-free diode lasers have shown improved performance in terms of output power 1 and long-term reliability. 2 Further, the fabrication of buried laser structures is facilitated in the absence of Al. However, the growth of GaInP and InGaAsP alloys on GaAs turns out to be challenging due to difficulties in growing thick ternary and quaternary layers that are precisely lattice-matched and due to miscibility and ordering problems. 3–5 These result in composition fluctuations and rough surfaces. To overcome these problems but to keep most of the advantages of the Al-free system we have combined GaInP waveguide layers with AlGaAs cladding layers for different types of diode laser structures. The formation of abrupt heterointerfaces between AlGaAs and InGaP is crucial for high power devices with good reliability. Several studies have characterized the GaInP/GaAs interface 6,7 and a quaternary intermedi- ate layer between GaInP and GaAs has been re- F. BUGGE, A. KNAUER, S. GRAMLICH, I. RECHENBERG, G. BEISTER, J. SEBASTIAN, H. WENZEL, G. ERBERT, and M. WEYERS Ferdinand-Braun-Institut für Höchstfrequenztechnik, D-12489 Berlin, Germany GaAs-based diode lasers for emission wavelengths between 800 nm and 1060 nm with AlGaAs-cladding and GaInP-waveguide layers were grown by MOVPE. For wavelengths above 940 nm broad area devices with InGaAs QWs show state-of- the-art threshold current densities. Ridge-waveguide lasers fabricated by selec- tive etching achieve 200 mW CW monomode output powers. (In)GaAsP QW- based diode lasers with an emitting wavelengths around 800 nm suffer from problems at the upper GaInP/AlGaAs interface. Asymmetric structures with a lower AlGaAs/GaInP and an upper AlGaAs/AlGaAs waveguide not only avoid this interface but also offer better carrier confinement. Such structures show very high slope efficiencies and a high T 0 . Maximum output powers of 7 W CW are obtained from 4 mm long devices. Key words: Diode lasers, metalorganic vapor phase epitaxy (MOVPE), strained quantum well ported. 8 By optimizing the reactor design and reduc- ing memory effects the formation of intermediate layers can be suppressed. Despite this there are very few studies about the growth of GaInP/AlGaAs heterointerfaces for laser applications. 9 Two key processes affect the formation of the inter- face structure and morphology: indium carry-over or indium segregation in the case of AlGaAs grown on top of GaInP and As/P exchange. In this paper we discuss conditions for the growth of diode laser struc- tures both for typical Ridge Waveguide (RW) and Broad area (BA) lasers as well as for Distributed Bragg Reflector (DBR) and Real Index Self Aligned (RISAS) lasers that require 2-step epitaxy. We use a GaInP/GaAs/AlGaAs test structure for basic investi- gations of the heterojunction and apply the results obtained to optimize the growth of laser structures. MATERIAL GROWTH MOVPE growth was performed in a horizontal reactor at a total pressure of 70 hPa and a V/III-ratio of 100 for AlGaAs and 175 for GaInP. Starting mate- rials were pure arsine and phosphine, the trimethyl compounds of aluminum, gallium and indium with hydrogen being used as the carrier gas. Dimethyl zinc was used for p-type doping and disilane diluted in hydrogen for n-type doping. The structures were grown on (100) GaAs “epi-ready” substrates (VGF-