The effect of dead space on gain and excess noise in In0.48Ga0.52P pindiodes

Electron-initiated avalanche gain and excess noise were measured in In 0.48 Ga 0.52 P 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 In 0.48 Ga 0.52 P and GaAs using the SMC suggests that, for a given avalanche width, the dead space effect is less significant in In 0.48 Ga 0.52 P at any value of gain. It was also found that the ionization path length probability distribution function is broader in In 0.48 Ga 0.52 P, leading to higher excess noise.