InSb PHOTODETECTOR WITH DIFFERENT ANTI-REFLECTIVE COATINGS AND GOLD NANOFILM FOR MID-IR REGION

Abstract

Mid-IR pin diode photodetectors are small and concise devices used in spectropho tometry, thermal imaging systems and in military defence for remote sensing. The key principle of the generated photocurrent is the absorptance of light into the de vice. But, this portion is almost missing in most experimental studies. This thesis investigates extensive absorptance analysis in an InSb-based photodetector with dif ferent anti-reflective coatings (ARCs) and a gold nanofilm for enhanced absorption in the 3- 6 µm wavelength range. Absorptance study is also done for TE and TM polarized light. It has been found that Si3N4 and ZrO2 as ARCs with Au gives 45% more absorptance than with bare InSb for normal incidence. For TE polarized light, Si3N4 with InSb shows maximum absorptance at 0◦ of 64.33%. Similarly, For TM polarized light, TiO2 and InSb show maximum absorption at 70◦ of 59% which is 31.5% more than absorptance at 0◦. However, stand-alone InSb shows absorption of 77.67% for 80◦. Moreover, the steady-state responsivity and photocurrent of the device for different incidence angles are calculated. As, Si3N4 with InSb shows maxi mum absorptance at 0◦ for which the photocurrent is 1.11 A and responsivity is 0.11 A/W for optical power of 10µW.