Physical Design Fundamentals of High-Performance Avalanche Heterophotodiodes with Separate Absorption and Multiplication Regions

Minimal value of dark current in reverse biased p −n junctions at avalanche breakdown is determined by interband tunneling. For example, tunnel component of dark current be‐ comes dominant in reverse biased p −n junctions formed in a number semiconductor ma‐ terials with relatively wide gap Eg already at room temperature when bias V b is close to avalanche breakdown voltage V BD (Sze, 1981), (Tsang, 1981). The above statement is ap‐ plicable, for example, to p −n junctions formed in semiconductor structures based on ter‐ nary alloy I n0.53Ga0.47As which is one of the most important material for optical communication technology in wavelength range λ up to 1.7 μm (Tsang, 1981), (Stillman, 1981), (Filachev et al, 2010), (Kim et al, 1981), (Forrest et al, 1983), (Tarof et al, 1990), (Ito et al, 1981). Significant decreasing of tunnel current can be achieved in avalanche photo‐ diode (APD) formed on multilayer heterostructure (Fig. 1) with built-in p −n junction when metallurgical boundary of p −n junction (x =0) lies in wide-gap layer of heterostruc‐ ture (Tsang, 1981), (Stillman, 1981), (Filachev et al, 2010), (Kim et al, 1981), (Forrest et al, 1983), (Tarof et al, 1990), (Clark et al, 2007), (Hayat & Ramirez, 2012), (Filachev et al, 2011). Design and specification of heterostructure for creation high performance APD must be such that in operation mode the following two conditions are satisfied. First, space charge region (SCR) penetrates into narrow-gap light absorbing layer (absorber) and second, due to decrease of electric field E (x) into depth from x =0 (Fig. 1), process of avalanche multiplication of charge carriers could only develop in wide-gap layer. This concept is known as APD with separate absorption and multiplication regions (SAM-