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Abstract Demonstrated are antimony‐based (Sb‐based) separate absorption and multiplication avalanche photodiodes (SAM‐APDs) for X‐ray and gamma‐ray detection, which are composed of GaSb absorbers and large bandgap AlAsSb multiplication regions in order to enhance the probability of stopping high‐energy photons while drastically suppressing the minority carrier diffusion. Well‐defined X‐ray and gamma‐ray photopeaks are observed under exposure to²⁴¹Am radioactive sources, demonstrating the desirable energy‐sensitive detector performance. Spectroscopic characterizations show a significant improvement of measured energy resolution due to reduced high‐peak electric field in the absorbers and suppressed nonradiative recombination on surfaces. Additionally, the GaSb/AlAsSb SAM‐APDs clearly exhibit energy response linearity up to 59.5 keV with a minimum full‐width half‐maximum of 1.283 keV. A further analysis of the spectroscopic measurement suggests that the device performance is intrinsically limited by the noise from the readout electronics rather than that from the photodiodes. This study provides a first understanding of Sb‐based energy‐sensitive SAM‐APDs and paves the way to achieving efficient detection of high‐energy photons for X‐ray and gamma‐ray spectroscopy. 

The suppression of leakage current via surface passivation plays a critical role for GaSb‐based optoelectronic devices. In this Letter the authors carefully optimise the sulfur passivation parameters for improving the performance of GaSb p–i–n devices. Two competing processes are evaluated during the sulfur passivation process: the hydrolysis of HS^–ions that aide surface passivation and the re‐oxidation, respectively. Upon the optimisation of sulfur passivation parameters and subsequent encapsulation with atomic layer deposition Al₂O₃, the surface resistivity significantly increased from 4.3 kΩ.cm to 28.6 kΩ.cm, leading to a 19.1 times drop in dark current at room temperature for the GaSb p–i–n structure. This Letter provides a repeatable and stable passivation approach for improving the optoelectronic performance of GaSb‐based devices.