Boundary effects on multiplication noise in thin heterostructure avalanche photodiodes: theory and experiment

Abstract

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the traditional thin-APD limit is predicted for GaAs, depending on the operational gain and the multiplication-region's width. The generalized model also thoroughly characterizes the behavior of dead space as a function of position across layers. This simultaneously captures the effect of the nonuniform electric field as well as the anticipatory nature of inter-layer bandgap-boundary effects. Such anticipatory behavior of the dead space is ignored in simplified models where the dead space is assumed to change abruptly at the layer boundary. The theory is applied to recently fabricated thin Al 0 6 Ga 0 4 As/GaAs heterostructure APDs exhibiting low excess noise factors. The excess noise factor predictions are in very good agreement with experiment. In one device, where the initial-energy effect is pronounced, the measured excess noise factor is 36% below the value predicted by previous analytical multiplication models which ignore the initial-energy effect.

High sensitivity 10Gb/s Si photonic receiver based on a low-voltage waveguide-coupled Ge avalanche photodetector

“…1(d). Hence, it is expected that strong avalanche multiplication can take place at moderate applied bias voltage, and that part of the avalanche excess-noise generation can be suppressed [6,[11][12][13]. …”

“…The total reduction of the power spectral density of the noise current in the presented device compared to a bulk Ge APD can be estimated as 35% for an avalanche gain of 10. This is attributed to the dead space effect in the thin avalanche multiplication region [6,[11][12][13]. …”

Gain-bandwidth product optimization of heterostructure avalanche photodiodes

“…Interestingly, the above effect was shown earlier to reduce the excess noise factor as well in a host of low-noise APDs (termed impact-ionization-engineered, , APDs) developed at the University of Texas. The low-noise characteristics of these bandgap engineered devices where shown to be a result of the initial energy effect using both analytical techniques [20], [21] as well as Monte Carlo simulation [16], [22]. We show in this paper that by carefully selecting the width of the energy buildup layer, the gain-bandwidth product can also be improved and optimized.…”

“…In order to account for the material and field inhomogeneity in the multiplication region, the pdfs and must incorporate: 1) the appropriate dead-space profile, which would accommodate the abrupt bandgap transition at the heterojunction and 2) the position-dependent ionization coefficients, which, in turn, depend on both the field value and the material at any specific location. In a hard-threshold dead-space model, the expressions for the pdfs are given by [20] (4) (5) The position-and material-dependent electron dead space is calculated using the following implicit equation [20]: (6) where is the electron ionization threshold energy for the material occupying the location . Similarly, the hole dead space is obtained using (7) In this paper, the model used to calculate the impact ionization coefficients, and , along with the threshold energies for electron and for holes (viz., , and ) correspond to those developed by Saleh et al [24] for GaAs and Plimmer et al [25] for Al Ga As, as shown in Table I.…”

Advances on Sensitive Electron-Injection Based Cameras for Low-Flux, Short-Wave Infrared Applications

“…They have typical noise factors of F ~ 4-5 (Feautriera et al, 2015). As such, huge amount of work has been reported in the literature to reduce the multiplication noise in such APDs (Saleh et al, 2000;Hayat et al, 2002;Kwon et al, 2003). Mercury Cadmium Telluride (HgCdTe) is the most important semiconductor alloy system for IR detectors in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral range and has addressed this issue.…”