Performance of Germanium and Silicon Surface Barrier Diodes as Alpha-Particle Spectrometers

Abstract

The characteristics of a germanium surface barrier diode operated at room temperature make it particularly useful as an alpha-particle spectrometer. The small size, stability, energy resolution, and relative insensitivity to {3 and 'Y radiation of the units suggest applications in medical and nuclear research. Studies were made on Au-Ge and Au-Si surface barriers with a barrier width (=:::1 Il) less than the range of the incident alpha particles. In the germanium units, the pulse-height response to alpha particles increased linearly with energy up to 7.5 Mev and then increased monotonically but more slowly as the energy rose to 12 Mev. In silicon the deviation from linearity occurred around 6 Mev. The observed linearity between pulse height and energy depends simply on the fact that the number of carriers excited is proportional to the particle energy and that the time for the carriers to be collected at the barrier is less than the circuit time constant. The general theory of the transient response of the diode was developed and the calculated response compared with the observed behavior. The observed values of the energy required to create a hole-electron pair, measured over the energy range of linear response of the junction, were '(Ge) = 2.96±0.1 ev and f(Si)=3.9±0.3 ev.

Gold contacts to semiconductor devices

“…Before we discuss the formation of the rectifying contact and its application in semiconductor integrated circuits we will give an overview of the nuclear particle detector. It was discovered nearly thirty years ago (12,13) that a gold layer on silicon or germanium could form an active region within the semiconductor thatwould respond linearly to the energy of an incident particle -in effect producing an alpha particle spectrometer. These detectors made an immediate impact on nuclear physics because of their compact size -centimetres as compared to the massive magnetic spectrometers -as well as their fast, linear response.…”

Geant4-based simulations of charge collection in CMOS Active Pixel Sensors

“…where D n is the electron diffusion coefficient and τ n is the charge carrier lifetime. Following [17] and using appropriate boundary conditions2 for equation (3.4), the solution of this equation at the collection electrode, as a function of the charge generation point z 0 , can be expressed as [18]:…”

3 Semiconductor Detectors

“…Surface barriers junctions were developed years ago for the detection of short range particles [80][81][82][83][84], They are still widely used to perform spectroscopy of α-particles, heavy ions, and fission fragments. Rectification is obtained by deposition of a metal producing a high Schottky barrier on the front side while the back contact may be formed either by means of a metal giving a low barrier height or by the diffusion of convenient impurities.…”