The current‐voltage characteristics and the bias dependence of the etch rates of <100>‐ and <111>‐oriented n‐ and p‐type low doped Si samples in aqueous KOH have been studied. We find that voltages cathodic of the open‐circuit potential have little effect on the p‐type etch rates, while the n‐type etching is stopped. Anodic of the open‐circuit potential, both carrier types stop etching, owing to passivation of the surface. These results are used to characterize the rate‐determining steps of the chemical or electrochemical reactions which take place at the semiconductor surface at various biases. A mechanism is proposed in which the rate‐determining step shifts between among chemical, electrochemical, or diffusion limited. Also, a mechanism involving susceptibility to nucleophilic attack is proposed to explain the vastly different etching rates of <100> and <110> vs. <111> faces.

Molecular hydrogen is alternately introduced into and removed from the gate oxide of irradiated metal-oxide-semiconductor field-effect transistors at room temperature by changing the ambient between forming gas (10/90% H2/N2) and nitrogen. Using charge pumping, it is observed that H2 causes a simultaneous buildup of interface states and decrease of trapped positive charge. The results are explained by a reaction sequence in which H2 is cracked to form mobile H+, which under positive bias drifts to the Si/SiO2 interface, and reacts to produce a dangling-bond defect. The rate limiting step over most of the time domain studied is the cracking process. Two types of cracking sites are modeled by molecular orbital calculations: oxygen vacancies (E′ centers) and broken bond hole traps (BBHTs). Initial- and final-state energies, as well as the activation energies, are calculated. The calculations indicate that the latter is the more likely H2 cracking site. The combined experimental and theoretical results suggest that at least 15% of the trapped positive charge is at sites similar to the BBHT sites. Implications of the model and similarities between interface-state formation by cracked H2 and irradiation are discussed.

The paths of basal plane dislocations (BPDs) through 4H-SiC epitaxial layers grown on wafers with an 8° offcut were tracked using ultraviolet photoluminescence imaging. The reduction of BPDs by conversion to threading edge dislocations was investigated at ex situ and in situ growth interrupts. For ex situ interrupts, BPDs are imaged after each of several growths. The wafer remains in the reactor for in situ interrupts and BPDs are imaged after the growth is finished. For in situ interrupts, a combination of temperature, propane flow, and duration has been determined, which achieve a BPD reduction of 98%.

The formation and expansion of recombination-induced stacking faults (SFs) within 4H–SiC bipolar and unipolar devices is known to induce a drift in the forward voltage during forward bias operation. This drift renders devices unsuitable for commercial applications. While the expansion of SFs in 4H–SiC occurs by the recombination-enhanced dislocation glide mechanism, why SF expansion occurs, i.e., the energetic driving force, remains unclear. Recent experiments have revealed that SF contraction and a recovery of the forward voltage drift can be induced under many conditions, including forward bias operation. Such observations have enabled the identification of SF-related degradation in devices where imaging methods are not possible and are inconsistent with the previously reported energetic driving force models. We present a model that qualitatively explains these recent experimental observations, which is based on the quasi-Fermi energy of the electron population during forward bias operation. Device simulation results and further experiments are also reported in support of this model.