Modified Surface Treatment

RMD’s researchers are continually trying to improve the performance of our APD detector technology; including enhancing the sensitivity and speed at wavelengths near the edge of the sensitivity range of silicon. This includes the ultraviolet (< 400 nm) and the near-infrared (> 1000 nm).

The Need

There are many applications that would benefit from silicon detectors with improved sensitivity in the UV and near-infrared. Modern Lidar systems often use advanced solid-state lasers because they provide short pulses with high peak powers in a rugged and compact design. The use of multiple wavelengths from a Nd:YAG laser (1064 nm, 532 nm, and 355 nm) has been of particular importance for aerosol and cloud analysis. While these transmitters have enabled great advances in satellite, airborne and ground Lidar systems, the development of matching receiver technology has lagged. In particular, few provide the necessary performance specifications at near-infrared and UV wavelengths.

RMD’s solutions

To meet this challenge, RMD is using specialized techniques to modify the surface of our detectors to increase the charge collection probability.

Near-infrared: We have used a surface texturing processes to enhance the sensitivity of our detectors from 950 to 1100 nm. The threefold improvement in the response we have achieved has resulted in best-in-class responsivity for our APDs.

Ultraviolet: With emphasis on 355 nm, a modified surface treatment has resulted in a four-fold improvement in bandwidth resulting in higher peak signals for Laser ranging applications.

(Left) Structured silicon surfaces developed by Harvard University have been used to enhance the near-IR efficiency of RMD’s detectors. (Right) Alternative modifications have been used to improve the detection bandwidth of our large area detectors in the UV and blue range.