Abstract
We demonstrate low noise short wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) avalanche photodiodes (APDs). The SWIR GaSb/(AlAsSb/GaSb) APD structure was designed based on impact ionization engineering and grown by molecular beam epitaxy on a GaSb substrate. At room temperature, the device exhibits a 50% cut-off wavelength of 1.74 µm. The device was revealed to have an electron-dominated avalanching mechanism with a gain value of 48 at room temperature. The electron and hole impact ionization coefficients were calculated and compared to give a better prospect of the performance of the device. Low excess noise, as characterized by a carrier ionization ratio of ~0.07, has been achieved.
Highlights
Avalanche photodiodes (APDs) internally amplify charge carriers with an avalanche process while operating under a high reverse bias that can cause impact ionization compared to conventional p-i-n photodiodes
We demonstrate a short wavelength infrared (SWIR) APD structure based on an multiquantum well (MQW) structure consisting of 20 loops of bulk GaSb well layer and AlAsSb/GaSb T2SL structure barrier layer sandwiched between two highly doped contact layers
The AlAs0.10 Sb0.90 layer in the AlAsSb/GaSb superlattices is well lattice-matched to the GaSb substrate with antimony atoms in common with the substrate, which in turn can bring a great range of flexibility into the superlattice growth and design
Summary
Avalanche photodiodes (APDs) internally amplify charge carriers with an avalanche process while operating under a high reverse bias that can cause impact ionization compared to conventional p-i-n photodiodes. APDs can deliver a high sensitivity that is involved with a gain mechanism via avalanche multiplication, with several applications in the military and fiber-optic communication, imaging and commercial sectors [1,2,3,4]. For short wavelength infrared (SWIR) APDs, several material systems are implemented, including silicon, AlGaAs/InGaAsSb, InP/InGaAs, and HgCdTe (MCT) [5,6,7]. The spectral band between 1.5–2.6 μm of the SWIR range can be served further compared to InP/InGaAs or MCT. Lattice-matched InGaAs/InP can deliver highperformance APD devices operating in the 0.9-to-1.7 μm wavelength range. MCT, on the other hand, is the most mature material system for infrared technology, but it suffers from drawbacks due to bulk and surface instability and due to higher costs, for fabrication [8]
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