Gallium arsenide (GaAs) technology leads the implementation of high frequency
devices with superior performance. A vast number of optoelectronic applications
are based on the material owing to its direct and wide bandgap. Over the
years the number of these applications continues to grow but they remain highly
cost-ineffective partly due to the growth techniques and the presence of defects in
GaAs. These areas have been researched on intensively over the past four decades
with much controversy, particularly on the subject of the EL2 defect. This defect
plays an important role in the design and operation of GaAs based devices. It is
therefore important to understand its electronic properties and influence on device
Schottky barrier diodes (SBDs) were fabricated on n-type GaAs. The quality of the
contacts was evaluated using current-voltage (I-V) and capacitance-voltage (C-V)
measurements before and after exposing them to different processing techniques
and radiation types. Deep-level transient spectroscopy (DLTS) and Laplace deeplevel
transient spectroscopy (L-DLTS) were used to characterize the electrically active
defects in the material. Defects with almost similar emission rates which were
not observed in the past were identified using L-DLTS due to its high resolution.
I-V and C-V measurements on as-deposited Au/n-GaAs SBDs in the 80 ?? 480 K
range showed that the EL2 defect has a profound effect on the diode characteristics.
The influence of the defect caused the temperature dependent behavior
of the C-V barrier height to be split into two temperature intervals, each with a
unique temperature coefficient. Exposure of the devices to temperatures above 300 K resulted in the deterioration of their I-V characteristics. Permanent physical
modification of the SBDs was observed at 400 K and above.
Inductively coupled plasma (ICP) etching, Electron beam deposition (EBD) and
electron beam exposure (EBE) were observed to impact significantly on diode I-V
and C-V characteristics. ICP etching resulted in devices with a lower reverse leakage
current and high barrier height whereas EBD fabricated devices exhibited the
poorest characteristics. DLTS results revealed that processing introduced electrically
active defects in the bandgap. EBE induced defects had different electronic
properties to all the processing and radiation induced defects observed in previous
I-V and C-V characteristics of SBDs exposed to alpha and beta-particle irradiation
were identical to as-deposited samples. This demonstrated the radiation hardness
of GaAs. DLTS spectra of alpha-particle irradiated SBDs displayed the defect
peaks sitting on a skewed baseline which hampered accurate L-DLTS measurements.
In addition to the prominent irradiation induced defects, high energy
electron-irradiation was observed to induce defects with electronic properties similar
to those of the EL2.