In this paper, low frequency noise and dark current correlation is investigated as a function of reverse bias and temperature for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) HgCdTe homo-junction photodetectors. Modelling of dark current-voltage characteristics shows that the detectors have ohmic-behavior under small reverse bias, thus enabling further analysis of 1/f noise-current dependences with the empirical square-law relation (S _I ∼ I²) at different temperature regions. It is found that for the SWIR and MWIR devices, the total 1/f noise spectral density at arbitrary temperatures can be modelled by the sum of shunt and generation-recombination noise as S I ( T , f ) = [ α S H I S H 2 ( T ) + α G − R I G − R 2 ( T ) ] / f , with no contribution from the diffusion component observed. On the other hand, for the LWIR device the diffusion component induced 1/f noise that cannot be overlooked in high temperature regions, and a 1/f noise-current correlation of S I ( T , f ) = { α s [ I D I F F 2 ( T ) + I G − R 2 ( T ) ] + α S H I S H 2 ( T ) } / f is proposed, with a shared noise coefficient of α _s ≅ 1 × 10⁻⁹ which is close to that calculated for shunt noise. The 1/f noise-current correlation established in this work can provide a powerful tool to study the low frequency noise characteristics in HgCdTe-based photodetectors and to help optimizing the “true” detectivity of devices operating at low frequency regime.

Avalanche photodiodes (APDs) can amplify the weak optical signal as well as enable higher receiver sensitivity due to the internal avalanche gain, but the impact ionization process can also introduce the “excess noise,” which limits the practically achievable signal-to-noise ratio (or sensitivity) and gain-bandwidth product. Hg $_{{1} -{x}}$ CdxTe electron-initialed APDs (e-APD) have been demonstrated to exhibit high performance in terms of gain and excess noise at 77 K. Here, we discuss the gain and excess noise properties of multiple Hg $_{{1}-{x}}$ CdxTe e-APDs with different Cd compositions targeting at short-wavelength infrared (SWIR), mid-wavelength infrared (MWIR), and long-wavelength infrared (LWIR) band operating at various temperatures. It demonstrates that the gain of APDs increases as the temperature decreases and the cutoff wavelength of the devices increases, which is related to the decrease of electron effective mass, optical photon scattering rate, and bandgap of the materials. In addition, the low excess noise of less than 1.6 at high gains is also achieved for the devices over a wide range of temperatures. The large spin-orbit splitting energy ( $\Delta $ so) in comparison to bandgap energy is considered to be responsible for the observed pure electron avalanche and exceptionally low excess noise. This work may provide insight into the low-noise HgCdTe APDs and is beneficial for the future applications of high-temperature operating and high-performance optical receivers.

In this work, an In _0.53 Ga _0.47 As/GaAs _0.5 Sb _0.5 type-II superlattice(T2SL) based broadband photodetector with an optical spectrum response ranging from 250 nm to 2400 nm is demonstrated. The photodetector shows a low dark current density of $3.48\times 10^{-4}$ A/cm ² under the bias of −1 V and a specific detectivity (D*) of $1.59\times 10^{10}$ cm $\cdot $ Hz1/2/W at $2 ~\mu \text{m}$ at 293 K. A recessed window on the surface of the top P layer was fabricated to enhance the responsivity of ultraviolet (UV) and visible band. The UV and visible band quantum efficiency (QE) can increase by 40% with the recessed window.

Low-frequency noise spectroscopy (LFNS) is an effective tool to study the trap properties in infrared photodetectors which may cause the limitations of dark current, dark noise, and quantum efficiency as well. In this article, the trap levels of HgCdTe infrared detectors with different Cd compositions are investigated with LFNS. The defect levels within the bandgap have been identified. In addition, trap states with activation energy above the material bandgap are also found for Hg-vacancy doped mid-wavelength and long-wavelength infrared HgCdTe photodetectors due to the resonant states located above the conduction band edge. The method to eliminate these resonant states is also investigated.

This paper presents the characteristics of HgCdTe mid-wavelength infrared (MWIR) electron-initiated avalanche photodiodes (e-APDs) as a function of temperature under different biases. The devices show a low dark current density of the order of ${10^{ - 7}} \text{A/cm}^2$ at 80 K when the reverse bias voltage is below 4 V, with an exponential gain above 100 at − 8 V. Low excess noise factor of around 1.2 is also demonstrated for the devices at 80 K. The dark current and gain characteristics at different temperatures are analyzed, along with the device simulation results. A varied-temperature impact ionization model for MWIR e-APD devices is adopted based on the experimental results. In addition, a significant increase of the dark current in the APD device is observed at high temperature under large reverse bias, which can be associated with the local electric field redistribution due to the accumulation of holes in the depletion region at high temperatures. The analysis presented in this work paves the way to achieve a high operating temperature (HOT) of the HgCdTe APD with further optimization.

In this paper, a novelty bandgap gradient multilayer heterojunction (BGMH) HgCdTe long-wavelength infrared detectors (LWIR) to provide low dark current is designed and prototyped. The fabricated photodetector is comprised of a wide-bandgap gradient p-type cap layer and intrinsic region to optimize the tunneling and surface current, also with a long-wavelength infrared responsed narrow bandgap n-type bottom layer. The BGMH LWIR detector, with a 100% cutoff wavelength of 14 μm, realizes a low dark current density of 5.7×10 ^-4 A/cm ² under the bias of -0.2V at 78 K. The peak value responsivity of 5.16 A/W and specific detectivity (D*) of 3.83×10 ¹¹ cm·Hz ^1/2 /W are also completed at 10.3 μm. The results suggest that the device performs exceedingly well and achieves beyond the conventional homojunction device.