220
7 Electronic Defect States
(a)
-0.25
Si
0.0
0.25
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-0.5
Si/B
BM
AB
T d
T d
H
+
0
(b)
Fig. 7.44 a Energy for positions u of the hydrogen atom along the 111 direction for H + in pure Si (Si atom at
u = −0.25) and neutral hydrogen (B atom at u = −0.25). u is measured in units of
√
3a 0 . For all positions of the
hydrogen atom the positions of the other atoms have been relaxed in the calculation. Data from [707]. b Adiabatic
potential energy in the (110) plane for hydrogen in Si:B. ‘BM’ denotes the bond minimum site (high valence electron
density), C and C’ are equivalent for pure Si. Reprinted with permission from [707], ©1989 APS
Fig. 7.45 Schematic model for hydrogen in silicon forming a complex with a a shallow acceptor (boron, empty orbital)
and b a shallow donor (phosphorus, double-filled orbital)
Hydrogen has experimentally been found to also passivate shallow donors. The microscopic configuration is sketched in Fig. 7.45b. The hydrogen atom sits on the Si–AB (antibonding) position and forms
an electron-pair bond with the silicon atom. The donor, e.g. phosphorus, is left with a double-filled
p-orbital (lone pair) whose level is in the valence band and thus no longer contributes to conductivity.
(a)
[110]
[001]
[110]
(b)
Fig. 7.46 a Structure of the V–O complex (A center) in silicon. The black sphere represents the oxygen atom. Reprinted
with permission from [710], ©2004 APS. b Calculated ground-state structure for the V–O–H 2 center in silicon. Oxygen
is over the C 2 axis, and the two white spheres represent hydrogen. Reprinted with permission from [711], ©2000 APS
7 Electronic Defect States
(a)
-0.25
Si
0.0
0.25
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-0.5
Si/B
BM
AB
T d
T d
H
+
0
(b)
Fig. 7.44 a Energy for positions u of the hydrogen atom along the 111 direction for H + in pure Si (Si atom at
u = −0.25) and neutral hydrogen (B atom at u = −0.25). u is measured in units of
√
3a 0 . For all positions of the
hydrogen atom the positions of the other atoms have been relaxed in the calculation. Data from [707]. b Adiabatic
potential energy in the (110) plane for hydrogen in Si:B. ‘BM’ denotes the bond minimum site (high valence electron
density), C and C’ are equivalent for pure Si. Reprinted with permission from [707], ©1989 APS
Fig. 7.45 Schematic model for hydrogen in silicon forming a complex with a a shallow acceptor (boron, empty orbital)
and b a shallow donor (phosphorus, double-filled orbital)
Hydrogen has experimentally been found to also passivate shallow donors. The microscopic configuration is sketched in Fig. 7.45b. The hydrogen atom sits on the Si–AB (antibonding) position and forms
an electron-pair bond with the silicon atom. The donor, e.g. phosphorus, is left with a double-filled
p-orbital (lone pair) whose level is in the valence band and thus no longer contributes to conductivity.
(a)
[110]
[001]
[110]
(b)
Fig. 7.46 a Structure of the V–O complex (A center) in silicon. The black sphere represents the oxygen atom. Reprinted
with permission from [710], ©2004 APS. b Calculated ground-state structure for the V–O–H 2 center in silicon. Oxygen
is over the C 2 axis, and the two white spheres represent hydrogen. Reprinted with permission from [711], ©2000 APS