DOPANT INCORPORATION DURING LP-VPE OF GaAs

Une étude du dopage avec Te et S de couches épitaxiées de GaAs dans le système HCl-Ga-AsH3-H2 à des pressions réduites à été faite. Te était ajouté à la source de Ga et H2S injecté dans la région de dépôt. Pour les 2 dopants, la réduction de la pression d'H2 conduit à augmenter les concentrations de dopant dans les couches. L'utilisation de concentrations de la phase gazeuse plus grandes que celles donnant les plus forts dopages accessibles (3xl018 cm-3 pour S, 6x1018 cm-3 pour Te) conduit à des valeurs réduites de la mobilité des électrons. De ce comportement, nous concluons que l'incorporation des dopants continue sous une forme neutre au-delà de ces concentrations. Un modèle qualitatif décrivant les résultats obtenus sur l'incorporation des dopants est présenté.A study was made of the doping of epitaxial GaAs films with Te and S in the HCl-Ga-AsH3-H2 system at reduced pressures using Te added to the Ga source or H2S injected in the deposition region. For both dopants reduction of the H2 pressure leads to increased dopant concentrations in the films. The use of gas phase concentrations larger than those yielding the maximum attainable electron concentrations (3x1018 Cm-3 for S, 6xl0l8cm-3 for Te) leads to reduced values for the electron mobility. It is concluded from this behavior that the uptake of dopants continues in neutral form beyond these concentrations. A qualitative model describing the data on dopant incorporation is presented

Photonik - Material und Technologien. Teilvorhaben: Integration photonischer Bauelementstrukturen mittels MOMBE Abschlussbericht

Growth of GaInAsP device structures by MOMBE had to be optimized, especially for selective area epitaxy to realize monolithic device integration. In addition the potential of MOMBE for device production had to be explored. Laser structures with strained multiple quantum well layers (MQWs) had to be fabricated and compared to MOVPE structures in terms of device performance. Laser-waveguide integration and planar-selective laser structures had to be formed by selective area epitaxy. A wafer holder for homogeneous growth in single and multi wafer (3 x 2'') operation had to be developed. A variety of MQW laser structures were fabricated with GaInAsP and InAsP layers as well material, where a compressive strain up to 2% was achieved. The MOMBE laser results are comparable to best MOVPE data. High quality waveguide-laser couplings were accomplished by embedded selective area epitaxy of the waveguide structure. Furthermore selective growth of laser structures was investigated. The threshold current densities of these lasers are comparable to data from large area reference lasers. A novel indium free wafer holder was realized resulting in excellent layer homogeneity. For GaInAsP NQW structures a standard deviation of photoluminescence #DELTA##lambda#<2 nm was obtained across more than 90% of the wafer area in multi-wafer operation for each wafer, the wafer-to-wafer standard deviation was #DELTA##lambda#<4 nm. Hence a basis for industrial use of MOMBE has been established. The investigations were performed in close cooperation with the University of Ulm, a project partner. An internationally leading position has been reached by this project. An extension of these studies to laser-modulator integration is planned for the future. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(70,42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman