Maskless lateral epitaxial overgrowth of GaN on sapphire

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20104728

Fini, P; Marchand, H; Ibbetson, J P; Moran, B; Zhao, L; Denbaars, S P; Speck, J S; Mishra, U K

The authors demonstrate a technique of lateral epitaxial overgrowth (LEO) of GaN, termed maskless LEO, in which no mask is deposited prior to LEO regrowth. Instead, a bulk (> 2 {micro}m) GaN layer on sapphire is selectively dry etched, leaving {approximately} 5 {micro}m-wide stripe mesas oriented in the <10{bar 1}0>{sub GaN} direction, with a 20 {micro}m period. These stripes serve as seeds for LEO GaN growth, which proceeds from the tops of the stripes and expands laterally, resulting in a T, or overhang, morphology. As for LEO over an SiO{sub 2} mask, significant defect reduction (from {approximately} 10{sup 9} cm{sup {minus}2} to {approximately} 10{sup 6} cm{sup {minus}2}) is observed in cross-sectional transmission electron microscopy (TEM). Atomic force microscopy of the top surface of the LEO GaN reveals that no threading dislocations with screw component terminate at the surfaces of laterally overgrown regions. X-ray diffraction measurements reveal that the wings exhibit a crystallographic tilt away from the seed regions in an azimuth perpendicular to the stripe direction; the tilt angle ({approximately} 0.4--0.5{degree}) is relatively independent of growth temperature and wing aspect ratio.

• Research Organization: Univ. of California, Santa Barbara, CA (US)
• Sponsoring Organization: Office of Naval Research; US Department of the Air Force; Natural Sciences and Engineering Research Council of Canada
• OSTI ID: 20104728
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL DEFECTS
CRYSTAL GROWTH
EPITAXY
EXPERIMENTAL DATA
GALLIUM NITRIDES
MASKING