AVS 50th International Symposium
    Thin Films Wednesday Sessions
       Session TF2-WeA

Paper TF2-WeA9
Dual-Color UV/IR Photodiodes Based on AlGaN Grown on Si and SOS for Advanced Fire/Flame Detectors

Wednesday, November 5, 2003, 4:40 pm, Room 329

Session: Optical Thin Films and Photovoltaics II
Presenter: D. Starikov, University of Houston
Authors: D. Starikov, University of Houston
C. Boney, University of Houston
N. Medelci, University of Houston
R. Pillai, University of Houston
A. Bensaoula, University of Houston
Correspondent: Click to Email
Rugged and reliable fire/flame detector arrays can be developed through integration of mature Si-based photodetectors with the newer UV wide band gap semiconductor photodetector technology. A GaN/InGaN/GaN double heterostructure grown on Si is photosensitive in the range from near UV to near IR. The UV range provided by the nitride layers (235-365 nm) is extended into visible and IR regions (365-1100 nm) by a Si p-n junction formed during the growth of the AlN buffer on the Si substrate. Schottky barrier photodiodes based on AlGaN layers grown on Si (detector 1) and sapphire (detector 2) can further extend the UV range of the above described structure and will be the focus of this paper. The AlGaN structures were grown using RFMBE and were processed by Cl-based reactive ion etching in order to expose each layer in the multilayer structure, deposit ohmic and Schottky barrier contacts, and investigate the electrical and photovoltaic properties of each interface. The results from detector 1 indicate high responsivity in short UV wavelengths down to 275nm, confirming the 35% Al concentration as determined by independent transmittance measurements, and in 550nm and longer range. Measurements from the detector 2 show a response limited to the UV range with a cutoff of between 290nm and 300nm indicative of an aver age Al content of ~25%. The above results are currently being implemented in the development of UV/IR sensitive tandem structures fabricated on silicon-on-sapphire (SOS) substrates. Results on the SOS-based photodetector fabrication, testing, as well as optimization of the UV to IR ratio by modeling of the component pixel structure will be presented.