Structure and Metastabiltty of Muonium Centers in Semiconductors and their Simulation of Isolated Hydrogen Centers
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STRIUCTURE AND METASTABIIITY OF MUONIUM CENTERS IN SEMICONDUCTORS AND THEiR SIMULATION OF ISOLATED HYDROGEN CENTERS '1. ,. ESTLE*, R.F. KIEFLt, J.W. SCIINEIDERt, AND C. SCHWAB-" Physics Department, Rice IlUiversity, hiouston, TX 77251 t TRIUMF, Vancouver, B.C., Canada V6T 2A3
I Physics Institute, Uuivers-ity of Zurich, C(1180011 Zurich, Switzerland Centre tie Recherches Nucl6aires, Universit6 Louis Pasteur, 67037 Strasbourg Cedex, France
A BSTRACT The study of isolated hydrogen in semiconductors is difficult because of the tendency for hydrogen to form complexes. An alternative to direct studies of hydrogen is tle study of nitioniuli in semiconductors. In such experiments the mtuoii is essentially ai isotope of hydrogen with !th the mass of the proton. Twenty isolated muoniumn centers have beeni observed in tetralied rally- coor(litiatced crystals ranging from Si to the cupro(us halides. Muon level-crossing resonance has provided detailed information on neutral interstitial nl-oliiiiin located at a bond center iin Si (the analog of the hydrogen center seen yvEPR) and very near a bond center in GaP and( GaAs. This paper reviews these nieasurements and discusses the structures and their metastabilities. Comparison is made I,,UR for Si alid to tieoretical studies. Recent results on thIe metastable and stable inuoniium centers in CuCi are discussed.
INTRODUCTION Since the discovery that hydrogen passivates or neutralizes electrically-active ceut.ers in semiiconductors, hydrogen auth the mmmecliaiisins for passivation have been stiithied
extensively in Si, GaAs, and several other semiconductors[l.,2]. The ceiters formed (hiring passivation are couiplexes of hydrogen amid other impurities or defects. Quite a bit is known about these associated centers but until very recently there has been little direct ififormation aboit the natire of isolated hydrogen centers. These centers are of interest iii their own right and also because they are the precursors of the associates formied duriig passivation. Part of the reason that so little was known about hydrogemi centers was that no electron paramagnetic resonance (EPR) or electron nuclear dIou!ble resonance (EN DOR) studies had been reported. A very important recent development is the first aid still tlie onmly observatioin of EPRI from isolated hydrogen iin a semiconaductorl.31. The major ditficulty with studying isolated hydrogen is that its high diffusivity results in hyd rogem foriiing complexes rather t han remaiaiiiig isolated. Au alternative to the study of hydrogen is the study of muomnium (aii electroi bound to a positive ini1o1), which miay be regarded as a very light pseudoisotope of iydrogeii (,,n,, ,,l,,)[4,5l . The str,,ctu-es of i,,,ioi,,inn ceiters should be very close to those of hydlr gen. This is illustrated dramatically by thle one direct comparison that calI be imiade: an isolated hydrogen center observed in Si by EPR[3lwhich has the same structure as that (of a niiioniui center iii Si, as evidenced by I lte almiiost ideitical lIyperline paraiiietersihi
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