Optoelectronic Devices: Ill-Nitrides
M. Razeghi and M. Henini (Eds.)
© 2004 Elsevier Ltd. All rights reserved.
Chapter 1
Introduction
M. Razeghi^ and M. Henini''
^Department of Electrical and Computer Engineering, Center for Quantum Devices, Northwestern University,
Cook Room 4051, 2220 Campus Drive, Evanston, IL 60208-3129, USA
^School of Physics and Astronomy, University of Nottingham, NG7 2RD, UK
1.1. INTRODUCTION
Wide bandgap Ill-nitrides, including (AI,Ga,In)-N, have seen enormous success in their
development especially in the latest stages of the 20th century. Many substantial problems
had to be overcome before these materials could constitute useful devices. High density of
dislocations due to the lack of lattice-matched substrates and low doping efficiency were
the most challenging problems that researchers in this area had to face. At the beginning,
it was hard to believe that a material with a dislocation density in the order of 10^-
10^^ cm~^ would become the building block of many viable devices. However, thanks to
the hard work of researches in this field, today blue/violet light-emitting diodes and laser
diodes based on (Al,In,Ga)-N have been successfully commercialized. Blue/green LEDs
have already found their market in full-color LCD displays and traffic lights, while blue
LDs are expected to shortly replace red lasers in the current CD/DVD read/write systems.
The unique properties of Ill-nitrides lead to a range of applications from optoelectronic
devices to high-power electronics. The wide bandgap of GaN makes this material suitable
not only for light emitting source but also for high-temperature applications. GaN and its
alloys have the potential to form high power electronics such as transistors or thyristors.
UV solar-blind photodetectors based on AlGaN have been demonstrated by several groups
[1]. These detectors have applications in early missile threat detection and interception,
chemical and biological threat detection, UV flame monitoring, and UV environmental
monitoring. Due to the polar nature of the Ga-N bond, GaN does not possess inversion
symmetry. Thus, when GaN is subject to an alternating electric field, the induced
polarization is not symmetric. This property of GaN can be used in non-linear optics
applications such as second-harmonic generation [2]. The same lack of inversion
symmetry results in a huge piezoelectric field. There are some other conceivable
E-mail addresses:
[email protected] (M. Razeghi),
[email protected]
(M. Henini).