We are collaborating on the development of detectors based on AlGaAs and GaAs with the Avalanche Photodiode Group of the University of Sheffield.

The material AlxGa1-xAs is widely used in GaAs-based electronic and optoelectronic devices. Any composition of AlxGa1-xAs can be grown, lattice-matched, to GaAs substrates which are commercially available in diameters up to 150 mm. As a result, using current epitaxial wafer growth technologies high quality AlxGa1-xAs material of suitable thickness (several microns) is achievable with a low density of growth defects. With high quality material and large band gaps of high Al-content AlxGa1-xAs, e.g. 2.09 eV for Al0.8Ga0.2As, AlxGa1-xAs diodes tend to exhibit low intrinsic reverse leakage current at room and above room temperature without any device passivation. The large band gap of AlxGa1-xAs suggests it would be suitable as the basis for a soft X-ray detector able to operate at room temperature and above ( upto 100C).

Development of GaAs diodes is also part of our research. We have reported the X-ray results for diodes operating well above room temperature.

Publications

1. J.E. Lees, A.M. Barnett, D.J. Bassford, J.S. Ng, C.H. Tan, J.P.R. David, N. Babazadeh, R. B. Gomez, P. Vines, R. D. McKeag and D. Boe, Development of AlGaAs avalanche diodes for soft X-ray photon counting, IEEE conference on Room Temperatrure Semiconductor Detectors, Valencia, Spain, 2011
2. R. B. Gomes, C. H. Tan, J. P. R. David, J.E. Lees, and J. S. Ng, Avalanche gain distribution of X-ray avalanche photodiodes, IEEE conference on Room Temperatrure Semiconductor Detectors, Valencia, Spain, 2011
3. J. S. Ng, R. B. Gomes, N. Babazadeh, J.E. Lees, J. P. R. David and C. H. Tan, GaAs p-i-n diode for room temperature soft X-ray photon counting, IEEE conference on Room Temperatrure Semiconductor Detectors, Valencia, Spain, 2011
4. J.E. Lees, A.M. Barnett, D.J. Bassford, J.S. Ng, C.H. Tan, N. Babazadeh,
   R. B. Gomez, P. Vines, J.P.R. David, R. D. McKeag and D. Boe, Development of high temperature AlGaAs avalanche diodes for soft X-ray photon counting, J. Inst. 6 (2011) C12007
5. R. B. Gomes, C. H. Tan, J.E. Lees, J. P. R. David, and Jo Shien Ng, Effects of dead space on avalanche gain distribution of X-ray avalanche photodiodes, Submitted to IEEE Electron Devices 2011
6. A.M. Barnett,  J.E.Lees, D.J. Bassford, J.S. Ng, C.H. Tan, N. Babazadeh and R. B. Gomez, The spectral resolution of high temperature GaAs photon counting soft X-ray photodiodes, Nucl. Inst.Meth A 654 (2011) 336-339
7. C.H. Tan, R. Gomez, J.P.R. David, A.M. Barnett, D.J. Bassford, J.E.Lees, J.S. Ng, Avalanche gain and energy resolution of semiconductor X-ray detectors, IEEE Electron Devices 58 (2010) 1696-1701
8. A.M. Barnett, D.J. Bassford, J.E.Lees, J.S. Ng, C.H. Tan and R. Gomez , The temperature dependence of the avalanche multiplication process in Al 0.8Ga0.2As avalanche photodiodes at soft X-ray energies, Nucl. Inst.Meth A 629 (2011) 154-156
9. A.M. Barnett, D.J. Bassford, J.E.Lees, J.S. Ng, C.H. Tan and R. Gomez , Modelling results of avalanche multiplication in AlGaAs soft X-ray APDs,
   Nucl. Inst.Meth A, 626-627 (2011) 25-30
10. A.M. Barnett, D.J. Bassford, J.E.Lees, J.S. Ng, C.H. Tan and J.P.R. David, Temperature dependence of AlGaAs soft X-ray detectors, . Nucl. Inst.Meth A, 621 (2010) 453-455
11. J.E. Lees, D.J. Bassford, J. S. Ng, C. H. Tan, and J. P. R. David, AlGaAs diodes for X-ray spectroscopy, Nucl. Inst.Meth A, 598 (2008) 202 - 205. doi:10.1016/j.nima.2008.06.038