Avalanche multiplication and breakdown Al/sub x/Ga/sub 1-x/(x > 0.9)

Monte Carlo Simulation of Hot Carrier Transport in Heterogeneous Ge/${\rm Al}_{x}{\rm Ga}_{1-x}{\rm As}~(0\leq x\leq 0.8)$ Multilayer Avalanche Photodiodes

“…From our simulation it was found that in the Ge/Al x Ga 1−x As multilayer structures,β is significantly larger thanᾱ and theβ/ᾱ ratio increases with increasing Al content x as explicitly indicated in Table II. Theseβ/ᾱ ratios are larger than that in Ge and Al x Ga 1−x As [15], as well as those of other III-V materials.…”

“…6, determined from the MC simulation for a 2.5-μm-thick p-i-n, indicates that the breakdown characteristics of the Ge/Al x Ga 1−x As multilayer structures against the Al content x have similar trend as those in the Al x Ga 1−x As homojunctions. As pointed out in [15], the breakdown voltage V bd in Al x Ga 1−x As has a linear relationship up to x = 0.63, beyond which V bd has a shallower slope against x. This is because, the valley becomes less important in determining the V bd of Al x Ga 1−x As when Fig.…”

“…The occurrence of random events such as the termination of a carrier's free flight, selection of a scattering event, and the change in flight angle and momentum are determined by the random numbers generated. The strength of phonon scattering for electron and hole, λ e , and λ h , respectively, represented by energy-independent phonon scattering mean free path, and impact ionization rate in the homogeneous materials, are obtained by fitting to the experimental data for bulk Ge [3], [4] and Al x Ga 1−x As (x = 0, 0.3, 0.8) [12]- [15]. A summary of the fitted parameters are presented in Table I. In the simple MC model, effective parabolic bands were used to represent the conduction and valence bands.…”

“…The MC program was validated by simulating the multiplication factors as a function of reverse bias in Ge [3] and Al x Ga 1−x As (x = 0, 0.3, 0.6, and 0.8) [12]- [15] homojunctions with various thicknesses, where good agreement between simulation and experiment was obtained. Similar heterointerface treatments applied to the simulation of GaAs/Al x Ga 1−x As material system were found to produce excellent agreement between with the experimental avalanche multiplication values for GaAs/Al x Ga 1−x As multilayer heterojunctions with various thicknesses [11], [23].…”

Numerical simulation of impact ionization in Ge/AlxGa1−xAs avalanche photodiode

“…4 and 5͒, and found that ␤ / ␣ improves when x increases from 0 to 0.6 but starts to show saturation from 0.6 to 0.8, since the electron ionization coefficient in Al 0.8 Ga 0.2 As is only marginally lower than that in Al 0.6 Ga 0.4 As. 10,11 On the other hand, it was found that when the i-region thickness increases to above 300 nm, ␤ / ␣ reduces toward an average characteristic between the Ge and Al x Ga 1−x As because the effects of dead space becoming less significant when the device length becomes thicker. 22 Thin i-region is also expected to give lower noise due to a narrower ionization probability distribution, 23 the GaAs/ Al x Ga 1−x As APD with similar device dimension has been studied and reported in the literature 5,23,24 and has been shown to exhibit low excess noise.…”