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

Abstract

Impact ionization in Ge/AlxGa1−xAs p-i-n heterostructures has been studied using the Monte Carlo technique. The thin (<300 nm) Ge/AlxGa1−xAs single heterojunction structure was found to exhibit large hole (β) to electron (α) ionization coefficient ratio, owing to a higher β in the Ge layer and a lower α in the AlxGa1−xAs layer, together with the dead space effects. The Ge/AlxGa1−xAs avalanche photodiodes are attractive for applications where a wide wavelength detection range is required for compatibility with multiple sources such as in the emerging active optical cable and optical interconnect applications, as well as in the established optical fiber telecommunication systems.

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

“…In this paper, a simple MC program similar to that reported in the literature [8]- [11] was used to simulate hot carrier transport in Ge/Al x Ga 1−x As multilayer structures. The simple MC model has fewer fitting parameters than the full-band model but includes the key physical features that may be used to give clearer insight into the ionization process involving heterojunctions.…”

Velocity enhancement in APDs with sub-100-nm multiplication region

“…The need for high performance low noise optical detection in optical communication networks has demanded lowering APDs' excess (multiplication) noise that requires downscaling of APDs' multiplication regions [3,4]. Performance of a thin APD is limited by electrons/holes dead length, which covers a significant portion of its multiplication region width [5,6]. The dead length is a distance that carriers require to traverse along their trajectories in an electric field of strength F to gain sufficient energy enough to overcome its ionizing threshold energy (E th ) [7].…”

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

“…Since in practice the output characteristics arising from impact ionization depend on many details, including specific band structure of a given material and characteristics of the relaxation processes giving a particular form of the non-equilibrium distribution function, the problem of calculation, say, of the I-V characteristics, starting directly from a band structure model is in no sense easy, from both conceptual and technical points of view. Therefore, the most popular method for modelling is Monte Carlo [3][4][5][6][7][8][9][10][11][12][13] , but it is obviously dependent on a particular relation between the impact ionization rate and the a) Electronic mail: afanasiev.an@mail.ru energy of a hot electron initiating the process, W(E). Phenomenologically, the rate must grow like a power of the excess energy above a threshold,…”

“…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.…”