Instructor: H'A' Atwater

1
APh 183 Physics of Semiconductors and Devices
Tuesday and Thursday, 900-1030 am 104 Watson
Instructor H.A. Atwater Complement 2What
Changes the Bandgap?
2
Band structure of Si at 300 K.
3

• Temperature Dependences of Silicon
• Indirect and Direct Bandgap
• Temperature dependence of the energy gap
•       
• Eg 1.17 - 4.7310-4T2/(T636) (eV),
• where T is temperature in degrees K.
• Temperature dependence of the direct band gap EG2
•       
• EG2 4.34 - 3.9110-4T2/(T125) (eV)

4
Absorption spectrum of high purity Si
Macfarlane, G. G., T. P. McLean, J. E.
Quarrington, and V. Roberts, J. Phys. Chem.
Solids 8, (1959) 388-392.
5
Absorption spectrum of high purity Si
Sze, S. M., Physics of Semiconductor Devices,
John Wiley and Sons, N.Y., 1981
Jellison, Jr., G. E. and F. A. Modine, Appl.
Phys. Lett- 41, 2 (1982) 180-182
6
Si absorption edge at different doping levels
(T 300 K)

• Wolfson, A. A. and V. K. Subashiev, Fiz. Tekh.
  Poluprovodn. 1, 3 (1967) 397-404 (in Russian)

7
Electrical and optical energy gap narrowing in
Silicon with donor doping density
Van Overstraeten, R. J. and R. P. Mertens, Solid
State Electron. 30, 11 (1987) 1077- 1087.
8
Dependence of the Silicon Energy Gap on
Hydrostatic Pressure EgEg(0)-1.410-3P (eV)
9
Energy Gap Shift in Strained SnGe/Ge
Semiconductor HeterostructuresDeformation
Potential Theory

• Tetragonal distortion 2 components
• hydrostatic compression
• uniaxial elongation

3. R. People, Phys. Rev. B 32, 1405 (1985) R.
Ragan, Ph.D Thesis, California Institute of
Technology, 2002
1. J. Bardeen and W. Shockley, Phys. Rev. 80,
72(1950) 2. G.E. Kimball, J. Chem.Phys. 3, 560
(1935)
10
Band structure of GaAs at 300 K
11
GaAs Energy Gap Temperature Dependences Temperat
ure dependence of the energy gap Eg1.519-5.4051
0-4T2/(T204) (eV) where T is temperatures in
degrees K (0 lt T lt 103). Temperature dependence
of the energy difference between the top of the
valence band and the bottom of the L-valley of
the conduction band EL1.815-6.0510-4T2/(T204)
(eV) Temperature dependence of the energy
difference between the top of the valence band
and the bottom of the X-valley of the conduction
band EX1.981-4.6010-4T2/(T204) (eV)
12
GaAs absorption edge at 297 K at different
p-type doping levels
Casey, H. C., D. D. Sell, and K. W. Wecht, J.
Appl. Phys. 46, 1 (1975) 250.
13
T-dependence of the relative populations of the
G, L and X valleys in GaAs
Blakemore, J. S., J. Appl. Phys. 53, 10 (1982)
R123-R181
14
Franz-Keldysh Shift of Energy Gap in an Electric
Field (no excitons)
W. Franz, Z. Naturforsch. 13a, 484 (1958).
L. V. Keldysh, Zh. Eksp. Teor. Fiz. 34, 1138
(1958) Sov. Phys. JETP 7, 788 (1958).
15
Franz-Keldysh Shift of Exciton Energy Gap in
Electric Field
J. D. Dow and D. Redfield, Phys. Rev. B 1, 3358
(1970).
16

Quantum-Confined Stark Effect in Quantum Wells
D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C.
Gossard, W. Wiegmann, T. H. Wood, and C. A.
Burrus, "Electric Field Dependence of Optical
Absorption Near the Band Gap of Quantum-Well
Structures," Phys. Rev. B 32, 1043-1060 (1985).
17
Integrated DFB-EA Transmitter

• 10Gb/s module, Ith 20mA, Pmax 4mW _at_80mA ,
  extinction ratio 15dB for -2.5V.