N. Pushpa

An investigation of electron and oxygen ion damage in Si npn RF power transistors

Abstract The effects of 8 MeV electrons and 60 and 95 MeV oxygen ions on the electrical properties of Si npn RF power transistors have been investigated as a function of fluence. The dc current gain (h FE), displacement damage factor, excess base current (Δ I B=I Bpost−I Bpre), excess collector current (Δ I C=I Cpost−I Cpre), collector saturation current (I CS) and deep level transient spectroscopy trap signatures of the irradiated transistors were systematically evaluated.

50 MeV Li3+ ion irradiation effects on advanced 200 GHz SiGe HBTs

The total dose effects of 50 MeV lithium (Li3+) ions on 200 GHz (8HP) silicon–germanium heterojunction bipolar transistors (SiGe HBTs) are studied in total doses ranging from 300 krad to 10 Mrad. The different electrical characteristics, such as the Gummel characteristics, dc current gain (h FE), neutral base recombination, avalanche multiplication of carriers (M−1) and output characteristics (I C–V CE), were studied before and after Li3+ ion irradiation. The results of 50 MeV Li3+ ion irradiation on SiGe HBTs are compared with 60Co gamma irradiation results in the same dose ranges.

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

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.

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

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.

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

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.

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

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.

A comparison of 100 MeV oxygen ion and Co-60 gamma irradiation effect on 200 GHz SiGe HBTs (HF 12)

We have investigated the total dose effects of 100 MeV Oxygen ion irradiation on the dc electrical characteristics of Silicon-Germanium Heterojunction Bipolar Transistors (SiGe HBTs). The results of oxygen ion irradiation were compared with Co-60 gamma irradiation in the same total dose range (1 Mrad to 100 Mrad). The results show that even after 100 Mrad of total dose, the degradation in the electrical characteristics of SiGe HBT is acceptable from the circuit design point of view.

Evaluation of pelletron accelerator facility to study radiation effects on semiconductor devices.

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.

The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors

ABSTRACT The silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50 MeV Li3+, 80 MeV C6+ and 150 MeV Ag12+ ions in the dose range of 1–100 Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (ΔIB), DC current gain (hFE), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with 60Co-gamma irradiation result in the same dose range. A considerable increase in base current (IB) and a decrease in hFE and ICSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag12+ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li3+ and C6+ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100 Mrad irradiated transistors up to 500°C to analyze the recovery in different electrical parameters. The hFE and other electrical parameters of irradiated transistors were almost recovered after 500°C for 50 MeV Li3+, 80 MeV C6+ ion and 60Co-gamma-irradiated transistors, whereas for 150 MeV Ag12+ ion-irradiated transistor, the recovery in electrical characteristics is not complete.

5 MeV Proton irradiation effects on 200 GHz silicon–germanium heterojunction bipolar transistors

ABSTRACT The total dose effects of 5 MeV proton and Co-60 gamma irradiation in the dose range from 1 to 100 Mrad on advanced 200 GHz Silicon–Germanium heterojunction bipolar transistors (SiGe HBTs) are investigated. The SRIM simulation study was conducted to understand the energy loss of 5 MeV proton ions in SiGe HBT structure. Pre- and post-radiation DC figure of merits such as forward- and inverse-mode Gummel characteristics, excess base current, DC current gain and output characteristics were used to quantify the radiation tolerance of the devices. The results show that the proton creates a significant amount of damages in the surface and bulk of the transistor when compared with gamma irradiation. The SiGe HBTs shows robust ionizing radiation tolerance even up to a total dose of 100 Mrad for both radiations.