The heteroepitaxy of Ge on Si: A comparison of chemical vapor and vacuum deposited layers

Epitaxial growth of Ge on Si has been investigated by two techniques: vacuum deposition and chemical vapor deposition (CVD). Vacuum-deposited Ge layers (physical vapor deposition, PVD) on heated Si substrates (≤ 500 °C) have smooth surface morphologies with a surface crystalline quality which improves with Ge layer thickness. Layers prepared by the CVD technique at 500–600 °C are comparable with the PVD prepared layers. Main defects in both PVD and CVD layers are dislocations initiating at the Ge/Si interface. Chemical vapor-deposited Ge layers grown at a substrate temperature of 700–800 °C exhibit poor crystalline quality and often are polycrystalline. Chemical vapor-deposited layers grown at a substrate temperature of 900 °C, again are good quality epitaxial layers. In this case, in addition to dislocations, stacking faults are present. All the studied layers are highly conductive and p-type. The conduction and valence band discontinuities determined from electrical measurements are 0.05±0.04 eV and 0.39±0.04 eV, respectively

Scanning Tunneling Microscopy and Tunneling Luminescence of the Surface of GaN Films Grown by Vapor Phase Epitaxy

We report scanning tunneling microscopy (STM) images of surfaces of GaN films and the observation of luminescence from those films induced by highly spatially localized injection of electrons or holes using STM. This combination of scanning tunneling luminescence (STL) with STM for GaN surfaces and the ability to observe both morphology and luminescence in GaN is the first step to investigate possible correlations between surface morphology and optical properties.Comment: 12 pages, Revtex 3.0, submitted to Appl. Phys. Lett., three figures available from Jian Ma at [email protected]

Electrically injected 164µm emitting In065Ga035As 3-QW laser diodes grown on mismatched substrates by MOVPE

We report the characteristics of the strained In0.65Ga0.35As triple quantum well (QW) diode lasers grown by metalorganic vapor phase epitaxy (MOVPE) on lattice-mismatched substrates such as GaAs or Si, by utilizing InP metamorphic buffer layers (MBLs) in conjunction with InAs nanostructure-based dislocation filters. As the lattice-mismatch between the substrate and InP MBL increases, higher threshold current densities and lower slope efficiencies were observed, together with higher temperature sensitivities for the threshold current and slope efficiency. Structural analysis performed by both high-resolution X-ray diffraction (HR-XRD) and transmission electron microscopy indicates graded and/or rougher QW interfaces within the active region grown on the mismatched substrate, which accounts for the observed devices characteristics