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

Abstract

Impact ionization in novel Ge/Al x Ga 1−x As (0≤ x ≤ 0.8) multilayer structures is investigated using numerical simulation. The simulated effective electron (ᾱ) and hole (β) ionization coefficients reveal that a largeβ/ᾱ ratio of up to 8 can be obtained in a 25-period Ge (50 nm)/Al 0.8 Ga 0.2 As (50 nm) multilayer structure, much larger than that in the Ge and Al x Ga 1−x As homojunctions, attributed by the reduction inᾱ. The substantial difference in phonon scattering cross-sections in the Al x Ga 1−x As barrier and the Ge well played an important role in determining theβ/ᾱ ratio in these structures. Breakdown voltage analysis indicates that hot carriers' drift in the Al x Ga 1−x As barriers and Ge wells sampled the transport properties of both materials, despite the electron and hole ionizations are dominated by that of Ge within the electric field range studied.

P-type Ge epitaxy on GaAs (100) substrate grown by MOCVD

“…The high hole mobility of pGe makes it one of the most suitable candidates for fabricating metal-oxide-semiconductor field effect transistor (p-MOSFET) and thus can replace silicon in the CMOS technology. Recent progresses indicated that p-i-n structures based on Ge/GaAs integrations could generate new possibilities for fabricating novel Ge/III-V based avalanche photodiodes (APDs) [22]. Detectors based on Ge can extend the cut-off wavelength of Si-APD (at 1.1 m) to 1.6 m while keeping the priority of low multiplication excess noise.…”

Competition between isotropic and strongly anisotropic terms in the impact ionization rate of narrow- and middle-gap cubic semiconductors

“…Appendix B: Approximate angular dependence of the quadratic term at arbitrary β Even thought an exact angular dependence of the quadratic term (23) at arbitrary β can be calculated only numerically, analytic approximation to it can be constructed via Pade-Borel method. For the cases of strong and weak spin-orbit coupling we have calculated series expansion of Eq.…”

“…Analytic expression for the cubic term can be found in the only paper by Gelmont et al 21 , but without any derivation. Thus, a proper analytic answer for W(E) has been inaccessible to the specialists in Monte Carlo modelling, so they prefer using some arbitrary values of the power n (and prefactor C) such as n = 2.5 and n = 4.3 22 , n = 5.2 3 , n = 3 4,6,23 , n = 3.9 24 , n = 1.85 25 . Some theoretical studies were focused on giving efficient recipes for the proper choice and numerical solution of the band models suitable for the realistic modelling 26,27 , but incorporation of the band calculations into Monte Carlo modelling seems too complicated to be practical.…”