Optimization of silicon planar lateral p-i-n diodes for NIEL measurements

The aim of this research is to investigate the possibility using of a planar p-i-n diode with variable base length as a displacement dose monitor. In the presented study, four planar lateral p-i-n diodes with a different length of i region fabricated on a common substrate were modeled and their response in terms of forward voltage bias change under 1MeV neutron irradiation has been studied theoretically.The I-V characteristics of the planar p-i-n structures taking into account variation of the diode’s parameters such as initial n-Si resistivity, recombination properties of n-Si, and geometry of the planar p-i-n structure have been simulated using the continuity equation. The effect of 1 MeV neutron irradiation on variation in the lifetime and mobility of the charged carriers and the effective doping concentration of the i region has been taken into account in the modeling of the I-V characteristics.The continuity equation was solved numerically under the condition of intermediate and high levels of injection of minor carriers into i region of the diode.The obtained solution allows optimization of the response of the planar lateral p-i-n diode by variation of initial characteristics of silicon, diode geometry and readout current density. For example, for the p-i-n diode with an i region length of 0.5 mm and typical parameters of 1 kOhm×cm n-Si, the diode response is linear up to neutron fluence Φ=10
¹²
cm
^-2
with the sensitivity of S~1×10
^-9
mV×cm
²
.The proposed compact planar lateral set of silicon p-i-n diodes which allow easy variation of i-region length in contrast to the bulk p-i-n diode can be attractive as a wide-range displacement damage dose sensor for various applications, including long-term space missions.