Growth Condition Dependence Of Rheed Pattern From GaAs (111)B Surface
- PDF / 1,141,628 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 63 Downloads / 170 Views
GROWTH CONDITION DEPENDENCE OF RHEED PATTERN FROM GaAs (111)B SURFACE
K. Yang*, W. Li', A. P. Taylor*, Q.-F. Xiao**, L. J. Schowalter', B. K. Laurich"**, and D. L. Smith-
* Center of Integrated Electronics and Department of Physics, Rensselaer Polytechnic Institute, Troy NY 12180 ** Department of Physics, State University of New York at Albany, Albany, NY 12222 * Los Alamos National Laboratory, Los Alamos, NM 87545
ABSTRACT A 3-dimensional phase diagram is introduced to describe the dependence of the RHEED pattern from GaAs(111)B surface on growth conditions. The 2x2, transitional(Ix1), and V/19x,/19 surface reconstructions correspond to different zones in the phase diagram. A equation is given for the planes that separate these zones, which fit experimental data well. Homoepitaxial films on GaAs(111)B grown in the 2x2 region generally have bad crystal quality as determined by the ion channeling, and growth in the V/19xV19 region generally yields rough surface morphology. At higher substrate temperatures (- 650 °C), featureless films with minimum ion channeling yields of less than 4% are achieved. INTRODUCTION Recently, more attention has been paid to the epitaxial growth on GaAs(111) substrates because the (111) orientation has several special properties. InGaAs/GaAs strained-layer superlattices (SLS) on GaAs(111) substrate have been predicted to have large linear electrooptic coefficients due to the strong piezoelectrically generated internal electric field.[1] Experimental studies on the optical properties of (100) and (111) oriented GaInAs/GaAs SLS have provided the evidence that agrees with the prediction.[2] In addition, Caridi et al. have fabricated p-i-n diodes grown on GaAs(111)B substrate by molecular beam epitaxy (MBE), with InGaAs in the intrinsic region. Photoconductivity spectra of such diodes show a blue shift of the quantum well band edge under reverse bias operation[3]. All this work indicates the possibility of fabricating novel electro-optical devices with a strong built-in electric field. High quality epitaxial films on GaAs(111) are crucial for turning this possibility into reality. Unfortunately, current understanding of epitaxial growth on the GaAs(111) surface, in comparison with that on GaAs(100), is poor and incomplete because only a limited number of studies have been done so far. Both homoepitaxial and heteroepitaxial films grown on GaAs(111)B, InAs(111)B, and InP(111)B usually show rough surface morphology, often exhibiting threefold pyramid, terrace, and other types of defects.[4,5,6,7] Hayakawa et al. have reported the achievement of specular surface on GaAs and AlGaAs films grown at 720 °C on 0.5' misoriented GaAs(111)B substrate at by MBE. Further, they showed that (111) oriented single quantum wells (SQW) have photoluminescence (PL) intensity about one order magnitude higher than (100) oriented SQW.[8] The threshold current density of the (111)B oriented quantum well laser is extremely low.[8,9] Imaota demonstrated that AlGaAs layers with featureless surface morphology can be gr
Data Loading...
