Low excess noise of Al0.85Ga0.15As0.56Sb0.44 avalanche photodiode from pure electron injection

Avalanche photodiodes (APDs) are used in optical receivers of high-speed optical communication systems to improve signal-to-noise ratio over conventional photodiodes. Low excess noise characteristics are crucial for APDs to preserve the benefits associated with high internal gains. In this work, we presented room temperature data of avalanche gain and excess noise factors of Al 0.85 Ga 0.15 As 0.56 Sb 0.44 APDs using pure and mixed carrier injection profiles. Using pure electron injection, the best possible excess noise performance for a given avalanche width was measured with an excess noise factor < 2 for gains up to 25. This is the lowest excess noise reported for this material system at high gain. Two other injection profiles with increased portion of injected holes worsened the excess noise performance, confirming the need to use pure electron injection for the best possible APD noise performance.