/
The investigation of high-per for mance AlGaAs/GaAs heterostr ucture bipolar tr ansistor s
NSC 90-2215-E-006-014
90 8 1 91 7 31
Abstr act
We have successfully fabricated
AlGaAs/GaAs
heterojunction
bipolar
transistor by MOCVD. Measurements
indicated t

11 NDR and Gunn Effect (Transferred Electron) devices
Gunn Diodes represent an example of negative differential resistance (NDR) devices
Why achieving the NDR is so attractive?
NDR
Load
Power dissipated in the diode = I2 x Rd < 0
The NDR diode can serve a

Silicon-Germanium
Heterojunction Bipolar Transistors
-An idea whose time has come
Ankit Goyal, IIT Roorkee
Tutor: Prof. S. Kal, IIT Kharagpur
Presentation Overview
y History, need of SiGe Technology
y Physics behind HBTs
y Bandgap Engineering
y SiGe Strai

ELCT 882- High-speed Semiconductor Devices
Instructor: Grigory Simin
simin@engr.sc.edu
High-speed Semiconductor Devices
The need for high-speed semiconductor devices:
Wireless communications high speed, high-power
transistors
Optical communications high s

09 Heterojunction FET (HFET) principles
MOSFET and HFET devices are both very
similar to a plain capacitor
Metal
A
V
d
Semiconductor
Let the area of the capacitor plates be A.
The induced charge Q can be expressed as
Q = q A nS,
where q = 1.6 10-19 C is t

14 Gunn Oscillators
Most of Gunn oscillators use the effect of high-filed domain instability
No domain
Domain propagates
Current-voltage characteristics of the Gunn diode
I-Vs are needed to design the oscillator circuits
Main characteristics of the stable

Waveguide structure of hetero-lasers
The Fabry-Perot etalon
Parallel mirrors
The separation between the mirrors is equal to an integer number of /2,
where is the wavelength of electromagnetic radiation.
In a laser, one of the mirrors partially transmits l

04 Heterojunctions (continued)
Example for the class work
Construct a band diagram for a (p) GaAs/(N) Al0.35Ga0.65As heterojunction at
thermal equilibrium.
The doping level and relevant material parameters are:
for the p-side GaAs, NA = 3 x 1019 cm-3;
and

13 Gunn Effect Amplifiers
I. Stable Gunn Diodes: I-V Characteristics
If the sample parameters do not meet the Kroemer criteria,
the sample is stable, i.e. the high-field domains do not form.
However, the differential mobility is still negative at high ele

20 Avalanche and Quantum Well Photodetectors
1. Avalanche Photodetector (APD) Principles
Ionization coefficient e h
Ionization coefficient e > h
The avalanche process is asymmetric (i.e., the probability for initiating an avalanche is usually
greater for

15 Transit Time and Tunnel NDR Devices
Schematics of Transit-time NDR diode.
A packet of carriers (e.g., electrons) is generated in a confined and narrow zone
(generation region) and injected into the adjacent fully depleted zone (drift region).
The curre

19 High-speed photodetectors
Photodetectors in high-speed communications
A photodetector is an optoelectronic device that absorbs optical signals and
converts them into electrical signals.
Light emitter
(Laser)
Optical link
Photodetector
(fiber or open a

06 BJT Performance limitations and HBT concept
Current gain limitations
The current gain limited by the injection into emitter,
Dn N de X e
o =
D p N ab W
The current gain limited by the recombination in the base,
R =
2L2nb
W2
The overall maximum common-e

03 Heterojunction Band diagrams and electrostatics
Some examples
After F. Schubert, RPI, 2003
03 Heterojunction Band diagrams and electrostatics
Some examples
After F. Schubert, RPI, 2003
03 Heterojunction Band diagrams and electrostatics
Some examples
Af

05 Bipolar Junction Transistors (BJTs) basics
The first bipolar transistor was realized in 1947 by Brattain, Bardeen and
Shockley. The three of them received the Nobel prize in 1956 for their
invention. The bipolar transistor is composed of two PN junctio

07 High Frequency Parameters of BJTs and HBTs
SMALL SIGNAL EQUIVALENT CIRCUITS
600
Base
current
1 A
Saturation
Active forward
400
2 A
3 A
4 A
5 A
200
0
-1.0
Cutoff
0
2.0
4.0
6.0
Collector-emitter voltage (V)
BJT I-V output characteristics. Also shown is a

02 Basics of Heterostructures
The limitations of homogeneous semiconductors and homo-junctions
The carrier transport cannot be controlled independently
02 Basics of Heterostructures
The limitations of homogeneous semiconductors and homo-junctions
Ec
n(x)

10 Universal HFET Model
Effect of Source and Drain Parasitic Resistances
RS
Ideal HFET structure
RD
Realistic HFET structure
The drain and source parasitic series resistances, Rd and Rs, play an important
role in limiting the device performance. These res