The tip of a scanning tunneling microscope was used to inject hot electrons across the gate and into the oxide of a metal-oxide-semiconductor structure. This method, known as ballistic electron emission microscopy ͑BEEM͒, allows an arbitrary choice of the energy of the injected electrons, which may be further accelerated by the application of a gate bias. The high current densities and choice of energy make BEEM an attractive method to study hot electron transport and breakdown phenomena in dielectrics. The studies reported here were made on Pd/SiO 2 /Si͑100͒ structures with a SiO 2 layer thickness of 3.8 nm. Monte Carlo techniques were used to calculate the spreading of the electron beam as it traverses the oxide. A strong dependence of the spreading on the kinetic energy and oxide thickness were observed. Using the calculated beam spreads to determine current densities and injected charge densities, the charge-to-breakdown ͑Q bd ͒ was measured for several breakdown sequences. The Q bd 's consistently exceeded by several orders of magnitude the values obtained by conventional Fowler-Nordheim ͑FN͒ tunnel injection under high field conditions. Most of the time, breakdowns could not be achieved for 3.8 nm oxides. It is concluded that impurity/ defects still control all observed breakdowns; an intrinsic limit-although claimed to have been reached-has not yet been established. Changes in the BEEM spectra with injected electron charge are interpreted in terms of a three stage process to breakdown: ͑I͒ electron trap creation and filling at the SiO 2 -Si interface, ͑II͒ prebreakdown believed to occur through thinning of the oxide that starts at the oxide-Si interface, and ͑III͒ oxide punch-through, characterized by an injection threshold Շ1 V, close to that for Si. The role of hot hole injection into the SiO 2 valence band was also assessed and deemed a negligible factor in the degradation process under the zero or low oxide biases used in the experiment reported here.

A silicon light source at the communication wavelength is the bottleneck for developing monolithically integrated silicon photonics. Doping silicon with erbium and oxygen ions is considered one of the most promising approaches to produce silicon light sources. However, this method suffers from a high concentration of defects in the form of nonradiative recombination centers at the interface between the crystalline silicon and large Er2O3/ErSi1.7 precipitates during the standard rapid thermal treatment. Here, a deep cooling process is applied to suppress the growth of these precipitates by flushing the high‐temperature Er/O‐doped silicon substrates with helium gas cooled in liquid nitrogen. The resultant light‐emitting efficiency at room temperature is enhanced by two orders of magnitude in comparison with that of the sample treated via standard rapid thermal annealing. The deep‐cooling‐processed Si samples are further processed into light‐emitting diodes. Bright electroluminescence with a main spectral peak at 1536 nm is also observed from the silicon‐based diodes with the external quantum efficiency reaching ≈0.8% at room temperature. Based on these results, the development of electrically driven silicon optical amplifiers or even lasers at communication wavelengths is promising for monolithically integrated silicon photonics.

The structural and electronic properties of the epitaxial Al/Si͑111͒7ϫ7 interface and their modifications upon thermal annealing were investigated by scanning tunneling microscopy, high-resolution photoelectron spectroscopy, and low-energy electron diffraction. Room-temperature deposition of 40 Å Al on Si͑111͒7ϫ7 is mainly characterized by epitaxial growth and a decrease of the Fermi-level position by 0.32 eV. Annealing at temperatures around 500°C results in the formation of large Al clusters with a thin reacted film in between. Subsequent annealing up to 900°C results in complete desorption of Al and a recovery of the original 7ϫ7 surface structure, while a potential variation underneath the Si surface, completely different from that of the starting surface, is observed in the Si 2p photoemission spectra. These results strongly indicate the formation of a p ϩ -Si layer induced by Al diffusion.

Degradation processes initiated by defect generation in device-grade SiO2 were studied by locally injecting hot electrons from a scanning tunneling microscope tip into Pd/SiO2/p-Si(100) metal–oxide semiconductor (MOS) structures. An analysis of the emerging collector current in the Si substrate, a technique known as ballistic electron emission microscopy, provides electron transport information, from which the oxide defect generation process was studied. The charging of the defects resulted in shifts of threshold energies for electron transport across the oxide. A novel sheet charge model was developed to assess the in-depth distribution and charge densities in the oxide from field-induced threshold shifts obtained from experiment. An as-fabricated MOS system with an oxide thickness of 71 Å was investigated and found to contain existing electron traps of charge densities in the range (0.7–2.8)×1013 e/cm2 that are distributed within a 30 Å region adjacent to the metal/oxide interface. Further stressing was performed at zero oxide bias with increasing tip voltages of up to −10 V. New electron traps characterized by charge densities of (1.9–3.6)×1013 e/cm2 and located within 40 Å of the SiO2/Si interface were generated when the kinetic energy of the electrons injected into the SiO2 conduction band exceeded 1.9 eV. This energy threshold is in very good agreement with the hydrogen-release energy that is frequently invoked to explain oxide degradation.

A novel method for the formation of a p+-layer underneath a Si(111)7×7 surface is presented. It is based on annealing of an epitaxial Al/n-Si(111) interface up to complete desorption of the Al film. This leads to a strong potential variation within the substrate, as observed in Si-2p core-level photoemission spectra with variable sampling depth, while scanning-tunneling microscopy reveals an unchanged 7×7 reconstructed surface. These observations are consistent with a p+ doping of (4±2)×1018/cm3 and a lowering of the surface Fermi level by (0.06±0.02) eV.