Research On The Proton And Electron Irradiation Effects Of InP-Based HEMTs

Space applications such as aerospace and satellite radar have determined the increasing demand for millimeter-wave radiation-resistant devices and integrated circuits.In P-based high electron mobility transistors?HEMTs?have excellent characteristics such as high frequency,high gain,low power consumption,and low noise,therefore,it is an excellent choice for millimeter-wave communication systems in space fields.However,the space environment is rich in protons and electrons,which are bound to pose a huge challenge to the space operation reliability of semiconductor devices and integrated circuits.The research on radiation damage mechanisms of In P-based HEMT has become an urgent problem to prompt its space applications.In this paper,the effects of defects caused by proton irradiation on the characteristics of In P-based HEMTs are discussed based on Sentaurus-TCAD software simulation and mathematical analysis models.And meanwhile,electron irradiation experiments under different fluences are carried on In P-based HEMTs and the degradation mechanism has been analyzed.The main contents and results of this article are as follows:1.Two-dimensional?2D?simulation physical model of In P-based HEMT is constructed by Sentaurus-TCAD.The hydrodynamic transport model and density gradient model are selected to describe the channel carrier transport process and the quantum effect inside the channel,and the simulated data fit well with the tested value.The slight difference in transfer characteristics may be due to the existence of surface states on the gate trench region of the actual device.Based on this,negatively charged surface-state defects are introduced on the gate-source and gate-drain surfaces of the device,and the effect of surface-state defect density is studied on the characteristics of In P-based HEMT.2.The influence of irradiation-induced defects on device characteristics is consistently calculated in Poisson equation and recombination model.On this basis,the effects of defect properties,including defect type,energy level,concentration on the characteristics of In P-based HEMT are studied by numerical simulations as well as the impacts of incident proton energy.The results indicate that only acceptor-like defects can significantly influence the device characteristics,and the device performances deteriorate more and more dramatically with the increase of defect concentration.The drain current decreases gradually with the increase of energy level with respect to the conduction band,and ultimately saturates at energy level distance of 0.5 e V.Additionally,low energy proton irradiation has a more severe effect on the characteristics of In P-based HEMTs.3.The proton irradiation effect on In P-based HEMTs has been studied with incident angle ranging from 0 to 89.9°.As the incident angle increases,the ultimate stopping position of incident protons gradually transfers from the buffer region to the hetero-junction region,and finally reaches the gate metal region.The 30^oincident proton terminates in the channel layer,and before that position the kinetic energy will be transferred to the lattice atoms and a large number of defects will be produced in the hetero-junction region by displacement effect.Therefore,30^oincident proton will causes serious degradation of drain current and transconductance.4.Under the condition of depletion approximation,an charge control analytical model was established with consideration of non-uniformly distributed vacancy defects.Analytical models of the channel electron concentration?n_s?,the direct current?DC?and radio frequency?RF?characteristics of In P-based HEMT were established based on the Poisson equation of In Al As material,the continuity equation of the electrical displacement vector at the hetero-junction interface,and the Gauss theorem of the In Ga As channel.Based on simulation,induced defects by proton irradiation are not uniformly distributed in the device structure.This paper introduces the induced defect distribution function into the charge control model and has discussed the device characteristics under different fluences.As the fluence increases,more As acceptor-like vacancies will be generated in the vicinity of the hetero-junction,and then more channel electrons will be compensated by the carrier removal effect,eventually causing more serious degradation of transconductance and frequency characteristics.In addition,the additional reverse modulation by present acceptor-like defects may shift the pinch-off voltage toward positive value.5.1 Me V electron irradiation experiments are performed on In P-based HEMTs under different fluences.?1?The characteristics degradation is quite slight with fluence of 1×10¹⁴cm^-2.However,with fluence increasing to 1×10¹⁶cm^-2,the saturation channel current,maximum transconductance,and on-resistance are degraded by 13.8%,12.9%and 10.2%,respectively.According to the charge control model,the carrier mobility gradually decreases with increased fluence while the carrier concentration barely increases.?2?The Kink effect decreases with the increase of the electron fluence.?3?The reverse gate current gradually increases with electron radiation fluence.Under the reverse bias,the Fermi level of semiconductor material at the interface might be below the defect level,which leads the defects to release electrons.Therefore,more electrons will pass through the Schottky barrier under larger radiation fluence.Additionally,the forward gate current decreases and the series resistance of gate contact increases with higher electron fluence,because the carrier mobility and concentration should become deteriorated by the induced defects in bulk materials and surface state defects at contact interface.?4?As the radiation fluence increases,the gate-drain capacitance(C_GD)and gate-drain capacitance/gate-source capacitance(C_GD/C_GS)increase,which thus results in a reduction in frequency characteristics.