High‐Performance Broadband Photodetector with Lateral Contact of n⁺‐Si Wafer by Two Asymmetric Work‐Function Electrodes

Abstract A high‐performance broadband photodetector (PD) has been fabricated by using a heavily doped n‐type silicon substrate (n + ‐Si) in a lateral photodiode geometry. This self‐biased photodiode fabrication required only two asymmetric work‐function electrodes deposited on top of a clean n + ‐Si substrate. Specifically, LiF/Al and MoO x /Ag are used as electrodes where LiF and MoO 3 work as n + ‐Si/electrode interface layers for Al and Ag electrodes respectively. These two electrodes have a work function difference of ≈1.1 eV which is measured by ultraviolet photoelectron spectroscopy study. Under dark, this lateral contact device shows a rectifying behavior with reverse‐to‐forward current ratio of ≈5.3 × 10 3 under ±1 V external bias. Moreover, this device shows a very high photoresponse with a dark‐to‐light current ratio (I L /I D ) of 2.15 × 10 4 under white light illumination (600 W m −2 ) at −1 V operating voltage. Besides, the device shows external quantum efficiency (EQE) of ≈16.1% under self‐biasing ( V ext = 0 V) conditions which reaches to 30.2% at −1 V external bias, whereas the device has responsivity (R λ ) and detectivity (D) of 10.2 A W −1 and 9.1 × 10 12 Jones, respectively under self‐biasing condition. The peak responsivity (R λ ) and detectivity (D) of these devices reaches to 17.5 A W −1 and 1.6 × 10 13 Jones under −1 V external bias.