AVS 51st International Symposium
    Semiconductors Wednesday Sessions
       Session SC-WeA

Paper SC-WeA5
Growth Modes of InN on Sapphire (0001) with GaN Buffer Layers

Wednesday, November 17, 2004, 3:20 pm, Room 304C

Session: Narrow Gap Semiconductors
Presenter: B. Liu, Lawrence Berkeley National Laboratory
Authors: S.R. Leone, University of California
B. Liu, Lawrence Berkeley National Laboratory
D.X. Chen, Lawrence Berkeley National Laboratory
T. Kitajima, National Defense Academy of Japan
Correspondent: Click to Email
InN is an important group-III nitride semiconductor. Use of InN can extend the working wavelength of the nitride-based optoelectronic devices from ultraviolet to infrared. However, heteroepitaxy of InN has encountered difficulties due to the thermal instability of InN and the large lattice mismatches between InN and the commonly used substrates (e.g., sapphire). During growth, the high equilibrium pressure of nitrogen requires a high V/III flux ratio to suppress InN decomposition, which often results in undesired three-dimensional (3D) rough surfaces. In this work, using atomic force microscopy (AFM) and scanning tunneling microscopy (STM), we study the growth modes and the surface morphologies of InN grown by plasma-assisted molecular beam epitaxy on sapphire (0001) substrates with intermediate GaN buffer layers. With smooth GaN buffer layers, 3D InN islands are observed to have mesa-like shapes with atomically flat tops. However, prolonged growth in this mode does not produce continuous two-dimensional (2D) InN films by coalescence of InN islands. With 3D rough GaN buffer layers, continuous 2D InN films are obtained showing the characteristics of step-flow growth. STM imaging reveals the defect-mediated surface morphology of the 2D InN films, including surface termination of screw (or mixed) dislocations and a high density of shallow surface pits with depths of about 0.1 nm. The mechanisms of the different growth modes and surface defect formation are also discussed.