Research On Graded Components AlGaAs/GaAs Nanowire Photodetector

Photodetectors, such as photo-multiplier tubes, silicon photodiodes and III/V materials-based photodetectors, have already found widespread applications in scientific instruments, optical communication, displaying and imaging, environment monitoring and security check. However, with the fast development of innovative technologies based on high performance photodetectors, an ever-pressing demand exists for photodetectors with higher sensitivity, smaller volume, and lower power consumption. Compared with traditional bulk materials, nanostructure photodetectors have attracted tremendous research attention for their small volume, high sensitivity and outstanding opto-electronic properties.A photodetection model for P+ and PN graded composition AlGaAs/GaAs nanowire photodetector is developed based on the numerical solution of coupled Poisson and continuity equations. Internal fields can strongly influence carrier statics and dynamics in semiconductor nanowires. The photocurrent and sensitivity of graded composition AlGaAs/GaAs nanowire photodetectors with different contact types as a function of incident light wavelength, Al composition range, and nanowire length, are simulated according to the model. The results demonstrate that a strong built-in electric field induced by graded composition in axial AlGaAs/GaAs NW, which can gain high carrier collection efficiency even under zero bias, and is very favorable to improve the photodetection performance. The photoelectric conversion property of PN type photodetector is better than that of P because of PN junction. Different electric fields induced by different contact types have distinct behaviors. The paper considers four types of two-terminal NW photodetector devices depending on the nature of the electrical contacts, namely, Ohmic-Ohmic(O-O) device, Ohmic-Schottky(O-S) device, Schottky-Schottky(S-S) device, Schottky-Ohmic(S-O) device. The results indicate that the Ohmic-Schottky devices have the highest sensitivities among four types of nanowire devices, while the Schottky-Ohmic devices have the least sensitivities. In this paper, inductively coupled plasma(ICP) etching was used to fabricate the P type AlGaAs/GaAs nanowire arrays. Using ultrasonic wave to break nanowires and select single nanowire under the microscope to make into device and test its photoelectric conversion performance.