26 6 2005 6 CHIN ESE J OURNAL OF SEMICONDUCTORS Vol. 26 No. 6 J une,2005 CdS/ CdTe 3 1 2 2 2 (1, 610031) (2, 610064) : CdS Cd Te,. (001) CdS/ Cd Te,. CdS/ Cd Te EV = 01 98eV 0105eV, Ec = 0107 01 1eV. : ; CdS/ Cd Te ; ; PACC : 8115 G; 7300 ; 7280 E : TN3041 2 + 5 : A : 025324177 (2005) 0621144205 1 Cd Te,, n CdS p Cd Te., Cd Te, CdS/ Cd Te., Ec Ev,,,. CdS/ Cd Te, [1 7 ]., Frit sche [ 1 ] Niles [2 ] Cd Te CdS, (300 400 ),., Ev = 0185 1eV, Ev = 0165eV. Ev = 1120eV [2 ].,, Frit sche CdS/ Cd Te, CdS ( ) / Cd Te Ev = 0193eV [1 ].,,. CdS/ Cd Te, SnO2 F/ CdS, Cd Te.,, CdS/ Cd Te, X ( XPS), CdS/ Cd Te. CdS/ Cd Te. 2 CdS/ Cd Te,, 1, [8 ]., 10-4 Pa, CdS (991999 %,Johnson2Matt hey) Cd Te (991999 %, Johnson2Matt hey), SnO2 F/,,..,. CdS/ Cd Te 3 ( :2003AA513010),1972,,. 2004208208,2004210225 Ζ 2005
6 : CdS/ Cd Te 1145,, L HC2 2, CdS/ Cd Te. 2 CdS/ Cd Te XRD Fig. 2 X2ray diffraction pattern of CdS/ Cd Te hetero2 junction 1 1 : ;2 : ;3,4 : Fig. 1 Schematic diagram of vacuum co2evaporation 1 :substrate ;2 :detector of quartz wafer ;3,4 :source XRD DX21000 X, 10 90, 0103 / s, Cu K, 01154184nm, 40kV,25mA. TU21901, 200 900nm, 015nm. X KRAOS CO XSAM800, Mg K, Au 4f 7/ 2 (84100eV) Ag 3d5/ 2 (3681 26eV). 3 CdS XRD Fig. 3 X2ray diffraction pattern of CdS films 3, SnO2 F/ 1 m CdS, 8nm Cd Te, 2. J CPDS, 2 23186 Cd Te (111),2 26162 54182 CdS(002) (004), (001) CdS/ Cd Te. 3 4 SnO2 F/ CdS Cd Te X. CdS, (001), 2 54182 (002). Cd Te, (111)., /, SnO2 F/ 4 Cd Te XRD Fig. 4 X2ray diffraction pattern of Cd Te films,. CdS,Cd Te, CdS,Cd Te 300nm. CdS, Cd Te ( 5, 6),,,,.
1146 26 10). : Cd Te,,.. 5 CdS Fig. 5 Optical transmittance spectrum of CdS films 7 CdS/ Cd Te XPS Fig. 7 X2ray photoelectron spectrum of CdS/ Cd Te heterojunction before etching 6 Cd Te Fig. 6 Optical transmittance spectrum of Cd Te films CdS,Cd Te,. h ( h - Eg) m, m = 1/ 2 ( ), CdS,Cd Te,CdS Cd Te 2141eV 1150eV, 100meV., ( 1mm) ( / / ),,,. 7, CdS/ Cd Te ( 2 ), Cd Te 8nm, S2p (,XPS 1 5nm)., C,O. 5min ( 8),C1s O1s, S2p S2s., XPS, CdS Cd Te S2p Te3d 161171 0105eV 572151 0105eV ( 9, 8 CdS/ Cd Te XPS Fig. 8 XPS of CdS/ Cd Te heterojunction after etching 9 S2p XPS Fig. 9 XPS of S2p core level of the CdS/ Cd Te hetero2 junction CdS Cd Te S2p 3/ 2 Te3d5/ 2 1591 97 01 05eV, 571175 0105eV [1 ], CdS Cd Te S2p Te3d, Ev = 0198 0105eV.
6 : CdS/ Cd Te 1147, CdS,Cd Te, CdS, (001) ; Cd Te, (111). CdS Cd Te 2141 011eV 1150 011eV. XPS, CdS/ Cd Te Ev = 0198 0105eV, Ec = 0107 011eV,. 10 Te3d XPS Fig. 10 XPS of Te3d core level of the CdS/ Cd Te het2 erojunction, CdS Cd Te, Ec = 0107 011eV,. ( ), CdS/ Cd Te Cd, [ 4 ], Ev = 0197eV [4,5 ] ;,, Harrison Ev = 0199eV [ 6 ] ;, Wei CdS/ Cd Te Ev = 0199eV [7 ].,Nishi CdS/ Cd Te Ec = 01098eV [3 ] ;, Frit sche CdS/ Cd Te Ev = 0193eV [1 ].. Niles [2 ], CdS, ;, (11 %),, ;,. 4 [ 1 ] Frit sche J, Thi en A, Klein A, et al. Oriented growt h and band alignment at the CdTe/ CdS interface. Thin Solid Films, 2001,387 :158 [ 2 ] Niles D W, Hochst H. Band off set s and interfacial properties of cubic CdS grown by molecular2beam epitaxy on Cd Te (110). Phys Rev B,1990,41 :2832 [ 3 ] Nishi K,Ohyama H,Siuzuki T,et al. Evaluation of t he CdS/ Cd Te interface using free2electron laser internal photoemis2 sion technique. Appl Phys Lett,1997,70 :3585 [ 4 ] McCaldin J O, Mc Gil T C, Mead C A. Correlation for 2 and 2 semiconductors of t he Au Schott ky barrier energy with anion electronegativity. Phys Rev Lett,1976,36 :56 [ 5 ] Tersoff J. Band lineups at 2 heterojunctions : Failure of the common2anion rule. Phys Rev Lett,1986,56 :2755 [ 6 ] Harrison W A, Tersoff J. Tight2binding t heory of heterojunc2 tion band lineups and interface dipoles. J Vac Sci Technol B, 1986,4 :1068 [ 7 ] Wei S H,Zhang S B,Zunger A. First2principles calculation of band offsets, optical bowings, and defects in CdS, CdSe, Cd Te,and their alloys. J Appl Phys,2000,87 :1304 [ 8 ] Shao Ye, Zheng Jiagui,Cai Daolin,et al. Preparation,proper2 ties and photovoltaic application of polycrystalline Cd1 - x2 Zn x Te thin films. Chinese Journal of Semiconductors,2003, 24 :183 (in Chinese) [,,,. Cd1 - x Zn x Te., 2003,24 : 183 ] CdS/ Cd Te
1148 26 Energy Band Discontinuity at Polycrystalline CdS/ CdTe Heterointerface 3 Huang Daihui 1, Wu Haixia 2, Li Wei 2, and Feng Lianghuan 2 (1 College of S cience, S outhwest J iaotong Universit y, Cheng du 610031, China) (2 College of M aterials Science and Engineering, S ichuan Universit y, Cheng du 610064, China) Abstract : The structural and optical properties of CdS and Cd Te films prepared by vacuum evaporation are studied by optical transmission spectra and X2ray diff raction measurement s. The CdS/ Cd Te heterojunction,whose CdS substrate is preferentially (001) oriented,is deposited in situ and characterized by X2ray diff raction and photoelectron spectroscopy before and after etch2 ing. From these measurements,the valence band off set is determined to be Ev = 0198 01 05eV and the conduction band off set is Ec = 0107 01 1eV. Key words : vacuum deposition ; CdS/ Cd Te heterojuntion ; valence band off set ; conduction band off set PACC : 8115 G; 7300 ; 7280 E Article ID : 025324177 (2005) 0621144205 3 Project supported by the High Technology Research and Development Program of China (No. 2003AA513010) Huang Daihui female,was born in 1972,lecturer. Her research interests focus on condensed matter physics. Received 8 August 2004,revised manuscript received 25 October 2004 Ζ 2005 Chinese Institute of Electronics