The effect of dead space on gain and excess noise in In0.48Ga0.52P p+in+ diodes
Electron-initiated avalanche gain and excess noise were measured in In0.48Ga0.52P p+in+ diodes, with avalanche region widths varying from 1 µm down to 0.1 µm, and also in a p+n+ diode. Hole-initiated gain is also measured in some diodes. We find that hole-initiated gain is only marginally higher than electron-initiated gain, indicating that the hole ionization coefficient is only slightly higher than the electron ionization coefficient. Electron-initiated excess noise is seen to fall as avalanche width is reduced. A simple Monte Carlo model (SMC) was used to interpret the results and to extract the ionization coefficients and effective threshold energies. A comparison between In0.48Ga0.52P and GaAs using the SMC suggests that, for a given avalanche width, the dead space effect is less significant in In0.48Ga0.52P at any value of gain. It was also found that the ionization path length probability distribution function is broader in In0.48Ga0.52P, leading to higher excess noise.