The growth, fabrication and characterization of high performance AI(formula)Ga(formula)N metal-semiconductor-metal photodiodes
Author
Bütün, Serkan
Advisor
Özbay, Ekmel
Date
2006Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
High performance UV photodetectors have attracted unwarranted
attention for various applications, such as in military, telecommunication, and
biological imaging, as an AlxGa1-xN material system is also rather suitable for
such applications. Its direct band gap covers the spectrum from 200 nm to 360
nm by way of changing the Al concentration in the compound. In this present
thesis, the design and growth of an Al0.75Ga0.25N template on sapphire substrate
and a deep-UV photodiode with a cut off wavelength of 229 nm that was
fabricated on the Al0.75Ga0.25N template is presented. A responsivity of 0.53
A/W was attained corresponding to a detectivity of 1.64 × 1012 cmHz
1/2/W at a
50 V bias and 222 nm UV light illumination. The UV/VIS rejection ratio of
seven orders of magnitude was achieved from the fabricated devices. The
second work that was conducted in this thesis was the growth of a semiinsulating
(SI-) GaN template. We also fabricated visible-blind photodetectors
on this semi-insulating (SI-) GaN template. Furthermore, we fabricated identical
samples on a regular GaN template in order to investigate any possible
i
improvement. The improvement found was obvious in terms of dark current. A
dark current density of 1.96 × 10-10
A/cm2
at a 50 V bias voltage for an SI-GaN
photodetector was obtained, which is four orders of magnitude lower than
devices on a regular GaN template. Devices on an SI-GaN had very high
detectivity, and therefore, SI-GaN was used for low level power detection. The
photogenerated current was well above the dark current that was under the
illumination of just a few picowatts of UV light.