Photocurrent Enhancement Between Two Coplanar Schottky-Barriers on Silicon MSM Photodetector

摘要

Gain properties of dc and ac photocurrent generated between two Schottky barriers collinearly placed on silicon metal-semiconductor-metal photodetector have been investigated experimentally. The test structure has two square Mo/n-Si Schottky barrier junctions on an n-type silicon substrate with a resistivity of 9-12 Ω-cm and the junction internal separation is 20 μm. The current-voltage (I-V) characteristics under illumination in visible range showed a rapid increase in the photocurrent at higher bias region. From the I-V characteristics and noise measurements, increase in photocurrent was ascribed to avalanche multiplication of carriers photogenerated in the reverse-biased Schottky junction. From observation of optical signal demodulation at low frequencies (10 kHz and 50 kHz), it was found that multiplication factor larger than 100 at 10 kHz and 30 at 50 kHz was achieved respectively.