A combination of electroless and electrochemical etching methods for enhancing the uniformity of porous silicon substrate for light detection application

摘要

This paper reports on a combination of electroless and electrochemical etching of a silicon surface for enhancing the uniformity of fabricated porous silicon substrate and improving the sensitivity of pho-todetectors. Photo-assisted pulsed electrochemical etching of silicon is modified by introducing a novel parameter called delay time (T_d), along with cycle time and pause time, of pulsed current, which can affect the morphology of pores. This technique offers the possibility of growing photoluminescent materials with uniform pores and selective wavelength emission. A sample with a T_d of 2 min shows a significant increase in the intensity of the Raman spectrum (10 times stronger than that of the sample without T_d at 518.2 cm~(-1)) due to the enhanced surface-assisted multi-phonon processes in porous film. A red-shift of 2.5 cm~(-1)and a peak broadening of 1.4 times are also observed for this porous sample compared with those of crystalline silicon. Porous surface properties and the performance of the optimized PS as photodetectors are discussed.