Characterization of GaSb photodiode for gamma-ray detection

Abstract

We extract the carrier mobility-lifetime products for epitaxially grown GaSb and demonstrate the spectral response to gamma rays of a GaSb p–i–n photodiode with a 2-µm-thick absorption region. Under exposure from 55Fe and 241Am radioactive sources at 140 K, the photodiode exhibits full width at half maximum energy resolutions of 1.238 ± 0.028 and 1.789 ± 0.057 keV at 5.89 and 59.5 keV, respectively. We observe good linearity of the GaSb photodiode across a range of photon energies. The electronic noise and charge trapping noise are measured and shown to be the main components limiting the measured energy resolutions.

Energy‐Sensitive GaSb/AlAsSb Separate Absorption and Multiplication Avalanche Photodiodes for X‐Ray and Gamma‐Ray Detection

“…The GaSb/AlAsSb SAM‐APD at reverse bias of 14 V shows a distinct peak at 59.5 keV with an FWHM of 1.283 ± 0.082 keV, which is much narrower than the 1.789 ± 0.057 keV of the GaSb PIN photodiodes (Figure b) in our previous report . In addition, we observe more signature energy lines, which are well‐defined and similar to the ones detected by the GaSb PIN photodiodes . Those energy lines include 1) Ga Kα escape peak at 50.3 keV; 2) Sb Kα escape peak at 33.2 keV; 3) Sb Kβ escape peak at 29.8 keV; 4) Sb Kα characteristic X‐ray peak at 26.3 keV; 5) Ga Kα escape peak at 17.1 keV; and 6) Ga Kα characteristic X‐ray peak at 9.3 keV.…”

“…The device responsivity was measured as 0.625 A W −1 using the primary photocurrent within this regime. This value is higher than the responsivity of 0.578 A W −1 given by the GaSb PIN devices . The improvement in responsivity can be attributed to the suppressed surface recombination due to additional AlGaSb window layers.…”

“…We acquired the second spectrum using another 241 Am source with a stronger activity (1.55 GBq) at 77 K, as shown in Figure a, to obtain better statistics at gamma‐ray energy . The GaSb/AlAsSb SAM‐APD at reverse bias of 14 V shows a distinct peak at 59.5 keV with an FWHM of 1.283 ± 0.082 keV, which is much narrower than the 1.789 ± 0.057 keV of the GaSb PIN photodiodes (Figure b) in our previous report .…”

“…A 50 nm Al 0.4 Ga 0.6 Sb (hereafter AlGaSb) layer was then introduced as surface barrier to eliminate the carrier loss . The same absorber thickness was used to match that of a previously reported GaSb PIN diode for a fair comparison of their spectroscopic performance evaluation . In this GaSb/AlAsSb heterostructure, the majority of the electric field can be tightly confined within the large bandgap AlAsSb multiplication region, while the magnitude of electric field is sufficiently low in the high‐ Z GaSb absorber.…”

“…Various photodetection systems for high‐energy photons have been developed in recent years with wide commercial and scientific applications . Among them, separate absorption and multiplication avalanche photodiodes (SAM‐APDs) composed of photoabsorbers and large bandgap multiplication regions are advantageous for achieving high‐efficient and low‐noise photodetection with high‐energy resolution .…”