Degradation Of Passivation Research Articles

Increased Front Surface Recombination by Rear-Side Laser Processing on Thin Silicon Solar Cells

We show the degradation of the front surface passivation by rear-side laser processing of thin silicon solar cells when using a laser with a pulse length of 8 ps. 45-μm-thick back-contact back-junction monocrystalline silicon solar cells show an energy conversion efficiency of 18.8% without rear-side laser processing, whereas they show only 7.5% with an additional rear-side laser process step for contact separation. This low efficiency is due to the degradation of the front surface passivation, which is confirmed by quantum efficiency measurements. The internal quantum efficiency at short wavelength is 0.88 without laser processing, whereas it is only 0.33 with the rear-side laser process step.

Effect of cladding layer and subsequent heat treatment on hydrogenated amorphous silicon waveguides

Although intrinsic hydrogenated amorphous silicon (a-Si:H) wire waveguides clad with normal SiO(2) layers have low propagation loss of 2.7 ± 0.1 dB/cm for transverse electric (TE) mode in the 1550-nm range, the transparency degrades when interfaced with other dielectrics (e.g., air) and/or exposed to elevated temperatures due to degradation of surface passivation in the a-Si:H waveguides. The thermal stability of a-Si:H wire waveguides with various cladding layers is systematically investigated, showing that the a-Si:H wire waveguides are stable at annealing temperature lower than ~350°C, while they degrade quickly when annealed at a higher temperature. It indicates that the thermal stability is mainly determined by the annealing temperature rather than the annealing time, which may be attributed to quick evolution of weakly bonded hydrogen in the a-Si:H waveguides. A thin Si(3)N(4) intercladding layer between SiO(2) cladding and a-Si:H waveguide core may degrade transparency due to N-H bond absorption and is of no benefit to the thermal stability, thus its overall effect on the a-Si:H waveguides is detrimental.

Reliability investigation of the degradation of the surface passivation of InAlN/GaN HEMTs using a dual gate structure

We analyze the degradation of InAlN/GaN HEMTs using a secondary gate electrode placed on top of the SiN passivation layer in between the Schottky gate and drain contact. Although the actual transistor showed only minor degradation during the stress test under off-state bias for more than 60h, a linear increase of trapped charges in the SiN layer has been detected starting at about 13h of stress. The charge increase is correlated with the increased leakage current and dielectric breakdown at the secondary gate.

Impact of Ionizing Radiation on the $\hbox{SiO}_{2}/ \hbox{SiC}$ Interface in 4H-SiC BJTs

Degradation of SiO2 surface passivation for 4H-SiC power bipolar junction transistors (BJTs) as a result of ion irradiation has been studied to assess the radiation hardness of these devices. Fully functional BJTs with 2700 V breakdown voltage are implanted with 600 keV helium ions at fluences ranging from 1 ×1012 to 1 ×1016 cm-2 at room temperature. These ions are estimated to reach the SiO2/ SiC interface. The current-voltage characteristics before and after irradiation show that the current gain of the devices starts degrading after a helium fluence of 1×1014 cm-2 and decreases up to 20% for the highest fluence of ions. Simulations show that the helium ions induce ionization inside the SiO2, which increases the interface charge and leads to a degradation of the BJT performance. Thermal annealing of the irradiated devices at 300 °C, 420 °C, and 500 °C further increases the amount of charge at the interface, resulting in increased base current in the low-voltage range.

Hydrogen Reintroduction by Forming Gas Annealing to LPCVD Silicon Nitride Coated Structures

The effect of high-temperature anneals on low-pressure chemical-vapor deposited (LPCVD) /thermally grown stacks on silicon wafers has been studied. Annealing in a nitrogen atmosphere at 900 or for causes a substantial reduction in both and bond concentration in the nitride film and a significant degradation of surface passivation. Subsequent anneals in forming gas (95% Ar/5% ) at temperatures in the range lead to a gradual reformation of and bonds and an improvement in surface passivation. It is hypothesized that the chief mechanism responsible for the improvement in surface passivation is the passivation of defects at the interface with atomic hydrogen, supplied by the breaking of and bonds in the nitride film. Samples with stacks display excellent surface passivation following high-temperature forming gas anneals, indicating that such treatments can be used for photovoltaic applications, where surface passivation as well as good optical properties are important.

Parallel hot-carrier-induced degradation mechanisms in hydrogen-passivated polysilicon-on-insulator LDD p-MOSFET's

Hot-carrier-induced stressing has been shown to degrade hydrogen-passivated p-channel polysilicon-on-insulator (poly-SOI) MOSFETs by two parallel degradation mechanisms. The authors observe hot-carrier-induced degradation of hydrogen passivation at grain boundaries through the creation of additional donor-type grain boundary states in the channel, as well as hot-electron trapping in the gate oxide. Due to the presence of both of these degradation mechanisms, p-channel polysilicon lightly doped source and drain (LDD) MOSFETs exhibit anomalous hot-carrier-induced degradation behavior that has not been observed in bulk p-MOSFETs. >