Multiple-wavelength emission from In/sub x/Ga/sub 1-x/As-GaAs quantum wells grown on a nanoscale faceted GaAs substrate by molecular beam epitaxy

Abstract

Multiple-wavelength photoluminescence (PL) spanning a 160-nm range from 980 to 1140 nm (77 K) has been obtained from In/sub x/Ga/sub 1-x/As-GaAs quantum wells (QWs) with varying In composition x on a nanoscale faceted (nanofaceted) GaAs substrate grown by molecular beam epitaxy. Five nanofaceted regions which consist of periodic [100]-(n11) (n = 3 or 1) facets along [011~] with different periods were prepared on a single substrate by interferometric lithography and selective growth of GaAs. The pattern period p was varied from infinity (large-area unpatterned) to 210 nm while the lateral width of the (n11) facet region was kept constant at /spl sim/180 to 200 nm within each period. A 5-nm-thick In/sub 0.23/Ga/sub 0.77/As layer was deposited on this multiple-period nanofaceted single GaAs surface in a single-run growth. Orientation-dependent migration and incorporation (ODMI) of In atoms [mass transport of incident In atoms from the (n11) to adjacent [100] facets] results in a variation of x of the In/sub x/Ga/sub 1-x/As layer section on the [100] facet as the width of the [100] facet was changed from /spl sim/20 to /spl sim/200 nm. ODMI induces a higher x on the [100] facet for smaller p. The PL exhibits a polarization dependence which is more pronounced for decreasing p [i.e., the width of [100] facet]. Consistent variations of the PL peak energy and linear polarization along the pattern direction confirm that ODMI results in a variation of the In composition and imply that the In/sub x/Ga/sub 1-x/As layer on a [100] facet has characteristics of a quantum wire as its width is decreased to /spl sim/20 nm for p = 210 nm. A possible application of nanopatterned growth to wavelength-division-multiplexing transmitters is discussed.