M Nakabayashi

Impact of neutron irradiation on optical performance of InGaAsP laser diodes

Abstract Results are presented of an extended study on the degradation and recovery behavior of optical and electrical performance and on induced lattice defects of 1.3 μm InGaAsP double channel planar buried heterostructure laser diodes with an In 0.76 Ga 0.24 As 0.55 P 0.45 multi-quantum well active region, subjected to a 1 MeV fast neutron and 1 MeV electron irradiation. The degradation of the device performance increases with increasing fluence. Two hole capture traps with near midgap energy level in the In 0.76 Ga 0.24 As 0.55 P 0.45 multi-quantum well active region are observed after a 1×10 16 n/cm 2 irradiation. These deep levels are thought to be associated with a Ga vacancy. The decrease of optical power is related to the induced lattice defects, leading to a reduction of the non-radiative recombination lifetime and of the carrier mobility due to scattering. The difference in radiation damage between 1 MeV fast neutrons and 1 MeV electrons is discussed taking into account the non-ionizing energy loss (NIEL). The radiation source dependence of performance degradation is attributed to the difference of mass and the probability of nuclear collision for the formation of lattice defects. The decreased optical power recovers by thermal annealing, and the recovery increases with increasing annealing temperature. The optical power recovers by 45% for 1 MeV neutron irradiation with a fluence of 1×10 15 n/cm 2 after a 300°C annealing.

Degradation and recovery of AlGaAs/GaAs p-HEMT irradiated by high-energy particle

Abstract Results of an extensive study on the irradiation damage and its recovery behavior resulting from thermal annealing in AlGaAs/GaAs pseudomorphic high electron mobility transistors (HEMTs) subjected to a 220-MeV carbon, 1-MeV electrons and 1-MeV fast neutrons are presented. The drain current and effective mobility decrease after irradiation, while the threshold voltage increases in positive direction. The decrease of the drain current and mobility is thought to be due to the scattering of channel electrons with the induced lattice defects and also to the decrease of the electron density in the two dimensional electron gas region. Isochronal thermal annealing shows that the device performance degraded by the irradiation recovers. The decreased drain current for output characteristics recovers by 75% of pre-rad value after 300°C thermal annealing for AlGaAs HEMTs irradiated by carbon particles with a fluence of 1×10 12 cm −2 . The influence of the materials and radiation source on the degradation is also discussed with respect to the nonionizing energy loss. Those are mainly attributed to the difference of particle mass and the probability of nuclear collision for the formation of lattice defect in Si-doped AlGaAs donor layer. A comparison is also made with results obtained on irradiated InGaP/InGaAs p-HEMTs in order to investigate the effect of the constituent atom. The damage coefficient of AlGaAs HEMTs is also about one order greater than that of InGaP HEMTs for the same radiation source. The materials and radiation source dependence of performance degradation is mainly thought to be attributed to the difference of mass and the possibility of nuclear collision for the formation of lattice defects in Si-doped donor layer.

Effects of mechanical stress on polycrystalline-silicon resistors

Abstract Results are presented of a study on the mechanical stress dependence of the resistance of polycrystalline silicon (Poly-Si) films doped with different atomic species, namely, with boron and phosphorus ions. B-doped films of 400 nm and P-doped films of 250 nm thickness were deposited by low-pressure chemical vapor deposition at 620 °C on thermally oxidized silicon wafers. A controlled amount of external stress was applied to the silicon wafers in order to investigate the impact on the electrical performance of the implanted Poly-Si resistors. The resistance of the B-doped Poly-Si films is shown to increase by the mechanical stress, while the resistance of the P-implanted Poly-Si films remained unchanged. It is concluded that this difference is related to the structural differences between Poly-Si films implanted with boron and phosphorus, respectively.

Impact of induced lattice defects on performance degradation of AlGaAs/GaAs p-HEMTs

Abstract Irradiation damage and its recovery behavior resulting from thermal annealing in AlGaAs/GaAs pseudomorphic HEMTs, subjected to 1-MeV electrons, 1-MeV fast neutrons and 220-MeV carbon, are studied. The drain current and effective mobility decrease after irradiation, while the threshold voltage increases in positive direction. The decrease of the mobility is thought to be due to the scattering of channel electrons with the induced lattice defects and also to the decrease of the electron density in the two-dimensional electron gas (2DEG) region.

Radiation damage of polycrystalline silicon films

The radiation damage of polycrystalline silicon (poly-Si) films, subjected to 20-MeV alpha ray, 20-MeV proton and 1-MeV electron irradiation, is studied. The degradation of the poly-Si films by irradiation is caused by the induced lattice defects in the grain itself rather than at its boundaries.

Defect assessment of irradiated STI diodes

The device performance degradation and the induced lattice defects of shallow trench isolation (STI) n þ p diodes, subjected to different high energy particle irradiations will be described. The diodes were irradiated with 1-MeV neutrons, 2-MeV electrons and 20-MeV protons. Insight into the displacement damage mechanisms is obtained by analyzing the relation between the current damage coefficient, and the calculated non-ionizing energy loss. Deep level transient spectroscopy is used to detect the radiation-induced electron capture levels. Some levels are thought to be related to the degradation of the STI interfaces. The degradation of the electrical performance results from the induced defects. A different degradation behavior in dependence of the irradiation particle is found for meander diodes compared with square diodes. 2002 Elsevier Science B.V. All rights reserved.

Radiation damage of N-MOSFETS fabricated in a BiCMOS process

Results are presented of a study on the radiation damage and its recovery behavior resulting from thermal annealing of n-MOSFETs fabricated in a 0.8-μm single-well BiCMOS process, subjected to γ-rays, 1-MeV electrons and 1-MeV neutrons. After irradiation, the base (substrate) current and interface trap density normally increase with increasing fluence. This result points out that both ionization damage in the gate oxide and lattice defects in the p-well are induced by the irradiation. The interface trap density recovers by 85% for γ-ray irradiation with a fluence of 1×108 rad, after a 300 °C annealing.

Radiation effect on n-MOSFETs fabricated in a BiCMOS process

Abstract Results are presented of a study on the radiation damage in n-MOSFETs fabricated in a 0.8 μm single-well BiCMOS process, subjected to 20-MeV protons. A comparison is made with the degradation behavior induced by γ-ray irradiation. Finally, the recovery under post-irradiation thermal annealing is also reported.

Influence of mechanical stress on the electrical performance of polycrystalline-silicon resistors

Results are presented of a study on the mechanical stress dependence of the resistance of polycrystalline silicon (Poly-Si) films, doped with different atomic species. Two types of Poly-Si film implanted with boron and phosphorus ions were studied, namely, B-doped films of 400 nm and P-doped layers of 250 nm thickness, which were deposited by LPCVD at 620 °C on thermally oxidized silicon wafers. Film doping was done by ion implantation at 50 keV, with a dose of boron and phosphorus of 2 × 1014 and 5.3 × 1014 cm −2 , respectively. The Poly-Si films were annealed in a H 2 ambient at 1000 °C for 20 min to activate the implanted atoms. A controlled amount of external stress was applied to the silicon wafers in order to study the impact on the electrical performance of the implanted Poly-Si resistors. The resistance of the B-doped Poly-Si films is shown to increase by the mechanical stress, while the resistance of the P-implanted Poly-Si films remained unchanged. It is concluded that this difference is related to the structural differences between Poly-Si films implanted with boron and phosphorus, respectively.