Performance of thin separate absorption, charge, and multiplication avalanche photodiodes

Abstract

Abstract-Previously, it has been demonstrated that resonantcavity-enhanced separate-absorption-and-multiplication (SAM) avalanche photodiodes (APD's) can achieve high bandwidths and high gain-bandwidth products while maintaining good quantum efficiency. In this paper, we describe a GaAs-based resonant-cavity-enhanced SAM APD that utilizes a thin charge layer for improved control of the electric field profile. These devices have shown RC-limited bandwidths above 30 GHz at low gains and gain-bandwidth products as high as 290 GHz. In order to gain insight into the performance of these APD's, homojunction APD's with thin multiplication regions were studied. It was found that the gain and noise have a dependence on the width of the multiplication region that is not predicted by conventional models. Calculations using width-dependent ionization coefficients provide good fits to the measured results. These calculations indicate that the gain-bandwidth product depends strongly on the charge layer doping and on the multiplication layer thickness and, further, that even higher gain-bandwidth products can be achieved with optimized structures.

Avalanche multiplication in Al/sub x/Ga/sub 1-x/As (x=0 to 0.60)

“…Furthermore, it is incapable of predicting the excess noise figures of thin GaAs and Al Ga As APD's as shown, for example, in [9], [10]. The overestimation of both the multiplication and the excess noise in thin structures by the LM has been explained by its neglect of the dead-space distance, where carriers have insufficient energy to initiate ionization.…”

Low multiplication noise thin Al/sub 0.6/Ga/sub 0.4/As avalanche photodiodes

“…Therefore the mixed carrier initiated multiplication process in the p in (n ip diodes will result in higher (lower) than for pure carrier injection in the thicker diodes. The values for the p in diode with 0.85 m are lower than those for GaAs and diodes with m [4], which fall on the curves with and 0.62 in (1) respectively. The reason for this is not clear at present but may be due to a larger ratio in .…”

“…Anselm et al [4] have measured the excess noise in for 0 and 0.2 and Li et al [6] have measured excess noise in for 0 and 0.3. The excess noise in for 0 to 0.3 was found to reduce with decreasing .…”

Equivalent circuit model of noise for a separate absorption and multiplication avalanche photodiode (SAM-APD)

“…8 [9]. For a low bias, all the shot noise curves are flat, and only near the breakdown voltage go up as the bias increases.…”

“…Fig. 5 shows the simulation results of the dark current with experiment results [9]. For low bias, the dark current is dominated by the diffusion current and the parasitic leakage current, and for high bias, the tunneling current plays an important role.…”