A129 Surface Science 168 (1986) 498-5/16 North-Holland, Amsterdam HETERO,1IUNCTION BAND DISCONTINUITIES FOR GaAs GROWN ON Ge(ll0): TIME VARIATION R.W. GRANT, J.R. WALDROP, S.P. KOWALCZYK and E.A. KRAUT Rockwell International Corporation, Microelectronics Research and Development Center, Thousand Oaks, CaliJ~)rnia 91360, USA Received 1(1 June 1985: accepted for publication 3 July 1985 The valence-band discontinuity, AE,, for heterojunctions formed by growing GaAs on epitaxial Ge(11(}) layers has bccn observed to exhibit a continuous decrease with time for --~ lll0 h after interface formation. These new results are compared with previous measurements for hctcrojunctions formed by growing GaAs on sputter-annealed Gc(11(1) substrates. It is found that the magnitude of the A E, variation and the associated time constant depend somewhat on interface preparation variables. Because the time-dependent zlEv variation is observed for GaAs grown on both epitaxial Gc(110) layers and on Gc(11(I) substratcs, it appears to be a characteris- tic feature of GaAs grown on Gc interfaces. Surface Science 168 (1986) 507-517 North-Holland, Amsterdam AMORPHOUS SEMICONDUCTOR HETEROJUNCTIONS: TECHNOLOGICAL IMPACT P. PERFETTI 1.s.M., CNR, Via E. Fermi 38, 00044 Frascati, Italy Received 10 June 1985; accepted for publication 14 June 1985 Examples of practical uses of photoemission techniques will be presented to explain open problems in heterojunction research of crucial technological importance. In particular, the negli- gible valence-band discontinuity found in the a-Si~ 5C~ 5:H/a-Si:H and a-SiN~.n:H/a-Si:H heterojunctions explain the high efficiency of a-Si:H p-i-n solar cells in which the p layer is replaced by the silicon-carbon or silicon-nitrogen alloy. Another interesting example of application of photoemission spectroscopy is the study of the SiOJa-Si:H interface. This study enabled us to unambiguously attribute the hydrogen sensitivity of the Pd/SiO~/a-Si:H hydrogen sensors to a hydrogen-induced built-in potential modulation. Surface Science 168 (1986) 518-530 North-Holland, Amsterdam DEFECTIVE HETEROJUNCTION MODELS J.L. FREEOUF and J.M. WOODALL IBM T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598, USA Received l(I June 1985; accepted for publication 14 June 1985 Fermi-level pinning behavior has been observed at the free surface, oxide interface, metal interface, MBE grown surface, stop-regrown homojunction, and misfit-dislocation pinned heterojunction of GaAs. Theories of such behavior are numerous and disparate. Theories of

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Page 1: Amorphous semiconductor heterojunctions: Technological impact

A129

Surface Science 168 (1986) 498-5/16 North-Holland, Amsterdam

HETERO,1IUNCTION BAND DISCONTINUITIES FOR GaAs GROWN ON Ge(l l0): TIME VARIATION

R . W . G R A N T , J . R . W A L D R O P , S .P . K O W A L C Z Y K a n d E . A . K R A U T

Rockwell International Corporation, Microelectronics Research and Development Center, Thousand Oaks, CaliJ~)rnia 91360, USA

Received 1(1 June 1985: accepted for publication 3 July 1985

The valence-band discontinuity, AE,, for heterojunctions formed by growing GaAs on epitaxial Ge(11(}) layers has bccn observed to exhibit a continuous decrease with time for --~ lll0 h after interface formation. These new results are compared with previous measurements for hctcrojunctions formed by growing GaAs on sputter-annealed Gc(11(1) substrates. It is found that the magnitude of the A E, variation and the associated time constant depend somewhat on interface preparation variables. Because the time-dependent zlEv variation is observed for GaAs grown on both epitaxial Gc(110) layers and on Gc(11(I) substratcs, it appears to be a characteris- tic feature of GaAs grown on Gc interfaces.

Surface Science 168 (1986) 507-517 North-Holland, Amsterdam

AMORPHOUS SEMICONDUCTOR HETEROJUNCTIONS: TECHNOLOGICAL IMPACT P. P E R F E T T I

1. s.M., CNR, Via E. Fermi 38, 00044 Frascati, Italy

Received 10 June 1985; accepted for publication 14 June 1985

Examples of practical uses of photoemission techniques will be presented to explain open problems in heterojunction research of crucial technological importance. In particular, the negli- gible valence-band discontinuity found in the a-Si~ 5C~ 5:H/a-Si:H and a-SiN~.n:H/a-Si:H heterojunctions explain the high efficiency of a-Si:H p-i-n solar cells in which the p layer is replaced by the silicon-carbon or silicon-nitrogen alloy. Another interesting example of application of photoemission spectroscopy is the study of the SiOJa-Si:H interface. This study enabled us to unambiguously attribute the hydrogen sensitivity of the Pd/SiO~/a-Si:H hydrogen sensors to a hydrogen-induced built-in potential modulation.

Surface Science 168 (1986) 518-530 North-Holland, Amsterdam

DEFECTIVE HETEROJUNCTION MODELS J . L . F R E E O U F a n d J . M . W O O D A L L

IBM T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598, USA

Received l(I June 1985; accepted for publication 14 June 1985

Fermi-level pinning behavior has been observed at the free surface, oxide interface, metal interface, MBE grown surface, stop-regrown homojunction, and misfit-dislocation pinned heterojunction of GaAs. Theories of such behavior are numerous and disparate. Theories of