Dark Current Analysis in InAs Quantum-dot APDs with Different Mesa Structures

초록

We investigated the changes in the dark currents in InAs quantum-dot (QD) avalanche photodiodes (APDs) with different shapes of mesas. The APDs were fabricated by using inductively coupled plasma/reactive ion etching (ICP/RTE) or H(3)PO(4) chemical etching. The dark currents (I(dark)) were observed to be 27 pA for the H(3)PO(4)-treated APD and 10 pA for the ICP/RIE-treated APD at -11 V at room temperature (RT). Then, to identify the effect of the mesas on the I(dark) of APDs, we measured the temperature-dependent (TD) I-V and C-V characteristics. As a result, we found that at temperatures below 200 K, the TD I(dark) of the H(3)PO(4)-treated APD was still 3 times larger than that of the ICP/RIE- treated APD, while the change of capacitance (Delta C) was 1.09 nF for the H(3)PO(4)-treated APD and 0.63 nF for the ICP/RIE-treated APD at voltages from 0 V to -12 V. These results indicate that the I(dark) of the APDs may be strongly affected by mesas and by the surface conditions of the device and that bulk tunneling and surface leakage shunt currents due to strong electric fields may be the dominant components that determine the I(dark) of the H(3)PO(4)-treated APD.

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