Transcript Document

In Search of a Practical Enhancement-Mode GaAs Based MOSFET Device
Experimental: Michael Hale, Sang I. Yi, D. Winn
Calculations: Jonathan Sexton
Advisor: A. Kummel
Gate
Approximation of the Density of States for Both
Clean and O Adsorbed GaAs(001)-(2x4)
dI/dV/(I/V) (a.u.)
Metal Oxide Semiconductor Field Effect Transistor
University of California, San Diego
Department of Chemistry, 0358
9500 Gilman Drive
La Jolla, CA 92093
+ bias (VD)
Oxide
Clean GaAs(001)-(2x4)
Unpinned
8
7
6
1.5eV
5
Fermi Level
4
3
p-type
In2O on GaAs(001)-(2x4)
21ºC Dose/Low Coverage
Low Energy Electron Diffraction Pattern
of a Monolayer of In2O on GaAs(001)-(2x4)
LEED Pattern Shows
(2x1) Periodicity
Source
n+
e- e- e- e- e- e- e- e- e- e- e- e- e- e- e-
Channel
16Å
8Å
n+
Drain
(n)
p-type
10
dI/dV/(I/V) (a.u.)
Deposited O atoms on GaAs(001)-(2x4)
•Showed bonding sites and explained why O atoms induce states within the band gap
Deposited Ga2O on GaAs(001)-(2x4)
•Showed a new surface order and explained why Ga2O passivates the surface
Deposited In2O on GaAs(001)-(2x4)
In2O on GaAs(001)-(2x4)
410°C Dose/Low Coverage
•Identified bonding sites and showed that the surface is unpinned
In2O Bonding in the Trough
Auger Electron Spectroscopy of In2O
on GaAs(001)-(2x4)
6
4
Monolayer Coverage of In2O
Ball and Stick Diagram
3
2
-2.0
-1.5
-1.0
-0.5
0.0
0.5
p-type Ga2O/GaAs
9
7
Fermi Level
5
3
1
-1
VB
-1.2 -0.9 -0.6 -0.3
CB
0.0
0.3
0.6
0.9
1.2
1.5
0
0
0
50Å
300Å
0
300Å
-1
Amorphous
& Rough
200
400
600
800
1000
1200
Fermi Level
-1.4 -0.7 0
Electron Energy (eV)
Sample Bias (V)
In2O on GaAs(001)-(2x4)
410°C Dose/High Coverage
Clean GaAs(001)-(2x4) Surface
Clean STM Image
10
9
8
7
6
5
4
3
2
1
0
Monolayer
Coverage
-3
-3.2
-2.0
-2.8
-2.5
-2.3
-1.1
-1.9
-1.7
-1.4
-1.2
-0.0
-0.8
-0.6
-0.3
0..1
0.1
0.3
0.5
1.8
1.0
1.2
1.4
1.6
2.9
2.1
2.3
2.5
3.7
3.0
3.2
3.4
3.6
4.8
4.1
4.3
4.5
4.7
5.9
5.2
5.4
5.6
6.8
6.0
6.3
6.5
6.7
9
0
dI/dV/(I/V) (a.u.)
As
-0.5
1.8
Electronic Measurements of In2O
on n-type GaAs(001)-(2x4)
Monolayer Coverage of Ga2O
O
0.5
1.0
300Å
Clean Ball & Stick Diagram
Monolayer Coverage
Line Spacing of In2O Vs. Ga2O
at Monolayer Coverage
Mulliken Charges for Ga20As20H32 with Ga2O
90
Ball and Stick Diagram
In2O
80
16Å
Percentage of Spacing
Auger Signal (a.u.)
Ga
1
Ga2O
70
60
50
-0.91
-0.14
-0.14
-0.14 -0.14
0.39
0.39
0.28
0.28
-0.13
-0.330.39
-0.13
0.39
-0.40
-0.40
-0.54
-0.13
-0.13
-0.33
-0.24
-0.24
-0.14
-0.38
-0.14
0.39
0.28
0.39
0.68
-0.35
-0.58
-0.35
-0.14 →-0.24
-0.24
-0.24
0.39
0.28
0.39
-0.14
-0.38
-0.14
40
30
20
10
0
16Å
2.3
CB
VB
Sample Bias (eV)
2
In
2.1
Fermi Level
5
In:O = 2:1
As, Ga
1.9
7
3.5
1.5
1.7
8
In2O Vs. Ga2O on GaAs(001)-(2x4)
410°C Dose/High Coverage
300Å
2.5
1.4
n-type Ga2O/GaAs
9
-2.5
93.8 eV
3
1.2
1.0
0.7
0.5
0.3
0.1
-0.2
-0.4
-0.6
-0.9
-1.1
-1.3
-1.5
Sample Bias (eV)
dI/dV/(I/V) (a.u.)
Oxide
8
After O Adsorption
6.5
Pinned
5
3.5
2
0.75eV
0.5
-1
-0.75
0 -0.1 0.2 0.4 0.7 0.9 1.1 1.4 1.6 1.9 2.1 2.3
-1.5 -1.3
-1.0 -0.8 -0.5 -0.3
Approximation of the Density of States for Ga2O
on Both n- and p-type GaAs(001)-(2x4)
+ bias (VD)
+ + + + + + + + + + + + + + + + + + + ++
-1.5
Unit Cell Has
(2x4) Periodicity
Metal Oxide Semiconductor Field Effect Transistor
+ bias (VG)
Gate
-1.8
n+
Drain
dI/dV/(I/V) (a.u.)
n+
Source
-2.0
2
16Å
0
800Å
8
10
12
14
16
18
Row Spacing (Å)
20
22 >24
Ga2O insertion restores surface As atoms to bulk-like charge