The temperature dependence performance of ultraviolet radiation detectors T. V. Blank, Yu. A. Goldberg, O. V. Konstantinov Ioffe Physico-Technical Institute of Russian Academy of Science, St. Petersburg, Russia IWORID 2002 AMSTERDAM

The temperature dependence of the quantum efficiency of GaP Schottky photodetectors. The fluctuation traps model. Comparison of the temperature dependencies of the quantum efficiency in Schottky and p-n photodetectors based on GaAs. The temperature dependence of the quantum efficiency of Si Schottky photodetectors. The temperature dependence of the quantum efficiency of 4H-SiC Schottky photodetectors. Conclusion. Outline Determination of photoelectric conversion process mechanism in Schottky photodetectors temperature stability of UV detectors A im

where  - quantum efficiency I- photocurrent Р - incident light power h - photon energy q- electron charge Experimental procedure

20 mm The temperature dependence of the quantum efficiency of GaP Schottky photodetectors The spectrum of the quantum efficiency  of GaP Schottky photodetectors at 300 K. The quantum efficiency  of GaP Schottky photodetectors as a function of the temperature for several photon energies. Au In h n-GaP 250  m cm -3

Optical losses where R is reflection coefficient  is dielectric constant Bulk losses Others losses surface recombination thermionic emission of thermalized and hot photoelectrons in the metal The effective optical length L of GaP as a function of the photon energy, 300 K, W is the width of the space-change region.

 =(1-R)  (1-  hot )(1-  thеrm ) 1-  thеrm =е -  /kT  =1  =(1-R)(1-  hot )е -  /kT, where  - quantum efficiency, R - reflection coefficient  - internal quantum yield  hot - loss factor of hot photocarriers  thеrm - loss factor of thermalized photocarriers  - activation energy of the localized photocarriers k - Boltzmann’s constant Т - temperature The fluctuation traps model a E c E v e c E c E v e h E c E v d e h h E c E v b Е = 0Е = 0 Е  0

Schottky and p-n photodetectors based on GaAs h p-AlGaAs 0,05  m p + -GaAs p-GaAs 0,4-0,7  m 5·10 18 cm -3 n-GaAs 1,0-4,0  m 1· ·10 17 cm -3 n-AlAs/GaAs BR, 12 periods n-GaAs substrate 2·10 18 cm -3 The spectrum of the quantum efficiency  of GaAs p-n photodetectors at 300 K. The spectrum of the quantum efficiency  of GaAs Schottky photodetectors at 300 K. Ni n-GaAs 10  m 2  cm -3 n + -GaAs 200  m  cm -3 In h

Comparison of the temperature dependencies of the quantum efficiency in Schottky and p-n photodetectors based on GaAs The quantum efficiency  of GaAs p-n photodetectors as a function of the temperature for several photon energies. The quantum efficiency  of GaAs Schottky photodetectors as a function of the temperature for several photon energies.

The temperature dependence of the quantum efficiency of p-n photodetectors based on Si The spectrum of the quantum efficiency  of Si p-n photodetectors at 300 K The quantum efficiency  of Si p-n photodetectors as a function of the temperature for several photon energies.

4H-SiC Schottky photodetectors The spectrum of the quantum efficiency  of 4H- SiC Schottky photodetectors at 300 K (line 1) and the spectrum of the relative effectiveness of different photon energies in bactericidal ultraviolet radiation (line 2). Cr n-4H-SiC 25  m 4  cm -3 4H-SiC cm -3 Cr h

The temperature dependence of the quantum efficiency of 4H-SiC Schottky photodetectors At 300KW=0.3  m L h ~1.4  m L th =W o +L h  1.7  m  =L -1  h ~4.5 eV where L is effective optical absorption length L th is threshold effective optical absorption length W is width of the space-change region L h is hole diffusion length  is absorption coefficient

The photoelectric conversion mechanism in 4H-SiC Schottky photodetectors Band structure of 4H-SiC and scheme of different optical transitions.

For Schottky photodetectors (based on GaAs, GaP, 4H-SiC) the quantum efficiency increases with temperature for all photon energies. For p-n photodetectors based on GaAs and Si the quantum efficiency is temperature independent in the region of intrinsic absorption. Near-surface imperfections manifest themselves as the fluctuation traps and have an influence on the photoelectric conversion process in Schottky photodetectors. Conclusion Future The temperature dependence of the quantum efficiency of p-n and Schottky photodetectors based on GaN. The temperature dependence of the quantum efficiency of not deep p-n photodetectors (based on 4H-SiC). External electric field Influence on the quantum efficiency for UV photodetectors.