K. C. Praveen

In Situ Investigation of Current Transport Across Pt/n-Si (100) Schottky Junction During 100

In situ current-voltage (<i>I</i>-<i>V</i>) analyses of Pt/n-Si (100) Schottky barrier (SB) diode are carried out during 100 MeV Ni⁺⁷ ion beam irradiation. The effect of MeV ion beam on the electrical parameters like ideality factor (η) and SB height (SBH) (φ_B) of SB diode is investigated. For lower fluences, SBH decreases from its preradiation value, but there is almost no change in SBH for ion fluences ranging from 5×10¹¹ to 1×10¹³ ions/cm². The reverse current is increased by about two orders of magnitude at the fluence of 5×10¹³ ions/cm² which corresponds to an exposure of a few tens of years in low earth orbit. The radiation-induced diffusion of Schottky metal into the semiconductor and creation of trap centers at the metal-semiconductor interface are supposed to be the most plausible mechanisms for these deviations in SB diode characteristics.

\hbox{MeV Ni}^{+7}

First-generation (50 GHz) silicon–germanium heterojunction bipolar transistors (SiGe HBT) were irradiated with 75 MeV boron ions and 100 MeV oxygen ions. The aim of the present investigation is to study the degradation of current–voltage (I–V) characteristics due to different linear energy transfer ions. The in situ I–V characteristics were measured before and after ion irradiation are forward mode and inverse mode Gummel characteristics, excess base current and current gain. It was found that the oxygen ion-irradiated SiGe HBT showed slightly more degradation when compared with boron ion-irradiated devices. The damage constant was calculated using the Messenger–Spratt equation, which confirmed more degradation in the case of oxygen ion-irradiated HBTs.

Ion Irradiation

The effects of 3 MeV proton irradiation on the I-V characteristics of NPN rf power transistors were studied in the dose range of 100 Krad to 100 Mrad. The different electrical characteristics like Gummel, current gain and output characteristics were systematically studied before and after irradiation. The recovery in the I-V characteristics of irradiated NPN BJTs were studied by isochronal and isothermal annealing methods.

In situ investigation of 75 MeV boron and 100 MeV oxygen ion irradiation effects on 50 GHz silicon–germanium heterojunction bipolar transistors

The electrical transport characteristics of a Au/n-Si metal-semiconductor Schottky barrier junction under exposure to 60Co gamma rays have been reported in this paper. The role of energy loss mechanisms in the Schottky junction due to gamma irradiation is studied using the current-voltage (I-V ) and capacitance-voltage (C-V ) measurements. The electrical characteristics were measured at various doses of gamma by incrementally increasing the exposure from 0.85 Mrad (Si) to 340 Mrad (Si) to systematically study the dose effects on electrical transport across the Schottky interface. After irradiation, the ideality factor was found to decrease initially up to a dose of 17 Mrad (Si), and thereafter, it started increasing. At a dose of 340 Mrad (Si), the characteristics of the Schottky interface were found to recover toward the pristine characteristics. The recovery effect is attributed to annealing of interface defects due to the electronic energy loss Se of gamma ray photons.

High total dose proton irradiation effects on silicon NPN rf power transistors

The third generation Silicon-Germanium Heterojunction Bipolar Transistors (200 GHz SiGe HBTs) were irradiated with 50 MeV Lithium and 75 MeV Boron ions in the dose ranging from 1 Mrad to 100 Mrad. The different electrical characteristics like forward-mode Gummel characteristics, inverse-mode Gummel characteristics, excess base current and current gain were studied before and after ion irradiation. The damage constants for 50 MeV Li3+ and 100 MeV B5+ ion irradiated SiGe HBTs were calculated using Messenger-Spratt equation.

Recovery of Electrical Characteristics of Au/n-Si Schottky Junction Under

ABSTRACT The total dose effects of 1 MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100 krad to 100 Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔIB), dc current gain (hFE), transconductance (gm), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (IB) and a decrease in hFE, gm and ICSat was observed after 1 MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1 MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C2) versus voltage shows that the effective carrier concentration and built-in voltage (Vbi) increase marginally upon 1 MeV electron irradiation. The results of 1 MeV electron irradiation were compared with 1 MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1 MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1 MeV proton-irradiated transistor. The 1 MeV proton, 1 MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.

{}^{60}\hbox{Co}

In this paper we present the comprehensive results on the effects of different radiation on the electrical characteristics of different semiconductor devices like Si BJT, n-channel MOSFETs, 50 GHz and 200 GHz silicon-germanium heterojunction bipolar transistor (SiGe HBTs). The total dose effects of different radiation are compared in the same total dose ranging from 100 krad to 100 Mrad. We show that the irradiation time needed to reach very high total dose can be reduced by using Pelletron accelerator facilities instead of conventional irradiation facilities.

Gamma Irradiation

The SiGe HBTs were irradiated with 80 MeV Carbon ions up to 100 Mrad of total dose and were subjected to mixed mode (MM) electrical stress. The DC electrical characteristics were studied for irradiated and MM stressed SiGe HBTs. The base current (IB) of the irradiated SiGe HBTs was significantly increased after 100 Mrad of total dose and in turn, decrease the current gain (hFE). A significant recovery in IB and hFE was observed for ion irradiated SiGe HBTs after MM stress. The recovery in electrical characteristics of the irradiated SiGe HBTs is mainly due to the raise in the junction temperature.

A comparison of 75 MeV boron and 50 MeV lithium ion irradiation effects on 200 GHz SiGe HBTs

The NPN transistors were irradiated with 80 MeV Nitrogen ion in the dose range from 100 krad(Si) to 100 Mrad(Si). The different electrical characteristics like Gummel characteristics, current gain(hFE) and output characteristics (IC-VCE) were studied before and after irradiation. After nitrogen ion irradiation a significant increase has been observed in the collector current (IC) along with increase in base current (IB). The hFE of the transistors decreased drastically after ion irradiation. Moreover, the output characteristics of the irradiated transistor show that the collector current (IC) in the saturation region (ICsat) decrease with increase in the ion dose.

Comparison of 1 MeV electron, Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

The 200 GHz SiGe HBTs were irradiated with 80 MeV Carbon ions up to a total dose of 100 Mrad to understand the degradation in electrical characteristics. The degradation in the electrical characteristics of SiGe HBTs was also studied by mixed mode electrical stress up to 10,000 s. The electrical characteristics were measured before and after every total dose and after fixed stress time. The normalized peak hFE of the stressed and irradiated SiGe HBTs are compared to estimate the equivalent stress time for a particular total dose. These correlations are drawn for the first time and the results will establish a systematic relation between stress time and total dose.