InAsxSb1-x (Indium Arsenide Antimonide) is an important low bandgap
semiconductor whose high quality growth on GaAs or Si substrates is
indispensible for low cost, large format infrared focal plane arrays (FPAs).
Quantum well infrared photodetector (QWIP) technology, relying on mature
semiconductors, is also promising for the above purpose. While AlGaAs/GaAs
has been the standard material system for QWIPs, the search for alternative
materials is needed for better performance. This thesis reports a detailed
investigation of molecular beam epitaxy grown mid-wavelength infrared
InAsxSb1-x photodiodes on alternative substrates, and long wavelength infrared
InP/InGaAs QWIPs.
In the first part of the study, InSb and InAs0.8Sb0.2 photodiodes grown on Si and
GaAs substrates are investigated to reveal the performance degrading
mechanisms due to large lattice mismatch. InAs0.8Sb0.2/GaAs photodiodes yield
peak detectivities of 1.4× / 1010 and 7.5× / 108 cmHz½ / /W at 77 K and 240 K,
respectively, showing that the alloy is promising for both cooled and near room
temperature detectors. Under moderate reverse bias, 80 K RoA product limiting
mechanism is trap assisted tunneling, which introduces considerable 1/f noise.
InSb/Si photodiodes display peak 77 K detectivity as high as ~1× / 1010
cmHz 1/2/W and reasonably high peak quantum efficiency in spite of large lattice
mismatch. RoA product of detectors at 80 K is limited by Ohmic leakage with
small activation energy (25 meV). Bias and temperature dependence of 1/f noise
is in reasonable agreement with Kleinpenning&rsquo / s mobility fluctuation model,
confirming the validity of this approach.
The second part of the study concentrates on InP/In0.53Ga0.47As QWIPs, and
640× / 512 FPA, which to our knowledge, is the largest format InP/InGaAs QWIP
FPA reported. InP/InGaAs QWIPs yield quantum efficiency-gain product as
high as 0.46 under moderate bias. At 70 K, detector performance is background
limited with f/2 aperture up to ~3 V bias where peak responsivity (2.9 A/W) is
thirty times higher than that of the Al0.275Ga0.725As/GaAs QWIP with similar
spectral response. Impact ionization in InP/InGaAs QWIPs does not start until
the average electric-field reaches 25 kV/cm, maintaining high detectivity under
moderate bias.
The 640× / 512 InP/InGaAs QWIP FPA yields noise equivalent temperature
difference of ~40 mK at an FPA temperature as high as 77 K and reasonably low
NETD even with short integration times (t). 70 K NETD values of the FPA with
f/1.5 optics are 36 and 64 mK under &ndash / 0.5 V (t=11 ms) and &ndash / 2 V (t=650 Rs) bias,
respectively. The results clearly show the potential of InP/InGaAs QWIPs for
thermal imaging applications requiring short integration times.
Keywords: Cooled infrared detectors, InAsSb, QWIP, focal plane array.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12606097/index.pdf |
| Date | 01 June 2005 |
| Creators | Ozer, Selcuk |
| Contributors | Besikci, Cengiz |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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