Characterization of single InP Nanowire-based Avalanche Photodetectors

Sammanfattning: Nanoscience is an emerging field of technology where the bottom-up fabrication techniques are utilized instead of the traditional top-down approaches for enhancing the performance of di erent optoelectronic devices. One such material is a semicon- ductor nanowire (NW) which holds immense potential in nanophotonic applications, such as solar cells, LEDs, lasers, sensors and photodetectors. In particular, detec- tion of infrared (IR) radiation emitted by all bodies has wide applications in medical imaging, environmental monitoring, surveillance, security and optical communica- tion. This Bachelor’s thesis fits in the purpose of developing novel devices which is part of a bigger project, aiming towards the fabrication and integration of e cient InP/InAsP NW Avalanche Photodetectors (APD). The NWs are designed with a Separate Absorption Multiplication (SAM) geometry in a vertical array pattern, but for a fundamental understanding single NWs are contacted in lateral geometry and characterized individually. The characterization setup used is a Cascade 11000B probe station equipped with a Keithley 4200 semiconductor characterization module. Our e orts were focused on determining experimentally the breakdown voltage for two di erent samples of NW APDs, as an initial step of establishing the dependance of the breakdown voltage with the temperature. A study of the contacts was also addressed in order to provide more data to the design of an optimized ohmic contact in the p-segment of the NWs. We could demonstrate that growing NWs with longer p-segments overcome the contacting issues previously reported. Additionally, we could recognize the influence on our results of the Schottky barrier present in the contact with the p+-segment, especially in the values obtained for the ideality factor (n = 1.2 ± 0.1 and n = 1.53 ± 0.12). Therefore, we conclude that optimizing the p-segment contact should be prioritized on further research. Finally, regarding the avalanche processes, the measurements performed were successful and in agreement with previous research on other materials. Nevertheless, the values obtained for the breakdown voltage (Vbr ≥ ≠45V on average) should be complemented with more measurements within the same samples, and with analysis on devices with di erent dopping profiles, in order to have a more reliable result and a trend in our data.