Performance of InxGa1-xAsyP1-yphotodiodes with dark current limited by diffusion, generation recombination, and tunneling

We present a theoretical study of the effects of diffusion, generation-recombination (GR), and the recently observed tunneling currents on the performance of photodiodes made from In
0.73
Ga
0.27
As
0.63
P
0.37
and In
0.53
Ga
0.47
As. Calculations are made for both p+ν and p-i-n punch-through diode configurations, and are compared with recent measurements made by several independent investigators. For doping densities typical of present material (
N_{D} \gsim 10^{15}
cm
^-3
), tunneling currents become dominant prior to avalanche breakdown. Thus, for detection of weak (-55 dBm at 45 Mbits/s) optical signals, the diodes must be operated at low voltages where GR is the dominant source of reverse-biased leakage. To meet the requirements of low capacitance (
C \leq 0.5
pF for a diode area of 10
^-4
cm
²
) and low GR dominated dark current (
I_{D} \leq 10
nA at
T = 70\deg
C), the doping density and effective carrier lifetime (τ
eff
) must be
N_{D} < 7 \times 10^{15}
cm
^-3
and
\tau_{eff} \gsim 150
ns for In
0.73
Ga
0.27
As
0.63
P
0.37
and
5 \times 10^{14} \lsim N_{D} \lsim 7 \times 10^{15}
cm
^-3
and
\tau_{eff} \gsim 3.5 \mu
s for In
0.53
Ga
0.47
As.