This work presents the modeling of light emission from silicon based p⁺n junctions operating in avalanche breakdown. We revisit the photon emission process under the influence of relatively high electric fields in a reverse biased junction ($>{10}^5$ V/cm). The photon emission rate is described as a function of the electron temperature $T_{\mathrm{e}}$ , which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range ($\lambda \sim$ 300–850 nm), where the peak wavelength and the optical intensity are both doping level dependent. It is theoretically derived that a specific minimum geometrical width ($\sim 170$ nm) of the active region of avalanche is required, corresponding to a breakdown voltage of ∼5 V, below which the rate of photon emission in the desired spectrum drops. The derived model is validated using experimental data obtained from ultra-shallow p⁺n junctions with low absorption through a nm-thin p⁺ region and surface coverage of solely 3 nm of pure boron. We observe a peak in the emission spectra near 580 nm and 650 nm for diodes with breakdown voltages 7 V and 14 V, respectively, consistent with our model.

A varactor diode configuration is presented for the implementation of low-distortion tunable matching networks, phase shifters, and filters. The configuration is based on varactors with an "exponential" C(V) relation in antiseries configuration with specific control voltage harmonic loading conditions. The resulting network combines a high capacitance tuning range with relatively low control voltages and excellent linearity. The linearity is independent of the applied control voltage and does not degrade at low tone spacing, which is ideal for the realization of adaptive transmitters and modulators. A specific N_dx-2 varactor doping profile is required for exact third-order intermodulation (IM3) cancellation. The remaining distortion is dominated by the much smaller fifth-order nonlinearities. The required impedance levels of the harmonic terminations are studied in terms of the maximum modulation bandwidth for which the proposed configuration remains linear. The doping profile optimization for quality factor, tuning range, and breakdown voltage is discussed. For experimental verification, the proposed varactor configuration has been implemented using a silicon-on-glass technology. The measurements demonstrate IM3 cancellation and indicate a superior linearity for modulated signals up to 10-MHz bandwidth.

A little more than a monolayer-thick pure-boron (PureB) layer was deposited on silicon at 250:C by chemical vapor deposition (CVD), forming junctions with low saturation current. They displayed the same efficient suppression of electron injection as PureB diodes fabricated with a few nm-thick PureB layer deposited at 400:C. Assuming a high concentrations of acceptor states at the B-to-Si interface, induced by a fixed negative charge in the range 5W1013 cm-2 to 5W1014 cm-2, would be consistent with the experiments and device simulations that exhibit an efficient suppression of electron injection. Metallization of the B-layers was studied, showing that in many situations thinning of the layer to monolayer thickness will lead to a significant increase in the electron injection.

Metallization layers of aluminum, gold, or copper are shown to be protected from interactions with silicon substrates by thin boron layers grown by chemical-vapor deposition (CVD) at 450 °C. A 3-nm-thick B-layer was studied in detail. It formed the p⁺-anode region of PureB diodes that have a metallurgic junction depth of zero on n-type Si. The metals were deposited by electron-beam-assisted physical vapor deposition (EBPVD) at room temperature and annealed at temperatures up to 500 °C. In all cases, the B-layer was an effective material barrier between the metal and Si, as verified by practically unchanged PureB diode I–V characteristics and microscopy inspections of the deposited layers. For this result, it was required that the Si surface be clean before B-deposition. Any Si surface contamination was otherwise seen to impede a complete B-coverage giving, sometimes Schottky-like, current increases. For Au, room-temperature interactions with the Si through such pinholes in the B-layer were excessive after the 500 °C anneal.

Sub-stoichiometric molybdenum oxide (MoO${}_x$ ) has recently been investigated for application in high efficiency Si solar cells as a “hole selective” contact. In this paper, we investigate the electrical and light-emitting properties of MoO${}_x$ -based contacts on Si from the viewpoint of realizing functional bipolar devices such as light-emitting diodes (LEDs) and transistors without any impurity doping of the Si surface. We realized diodes on n-type Si substrates using e-beam physical vapor deposition of Pd/MoO${}_x$ contacts and compared their behavior to implanted p${}^{+}$ n-Si diodes as a reference. In contrast to majority-carrier dominated conduction that occurs in conventional Schottky diodes, Pd/MoO${}_x$ /n-Si diodes show minority-carrier dominated charge transport with I–V, C–V, and light-emitting characteristics comparable to implanted counterparts. Utilizing such MoO${}_x$ -based contacts, we also demonstrate a lateral bipolar transistor concept without employing any doped junctions. A detailed C–V analysis confirmed the excessive band-bending in Si corresponding to a high potential barrier ($>0.90$ V) at the MoO${}_x$ /n-Si interface which, along with the observed amorphous SiO${}_x$ (Mo) interlayer, plays a role in suppressing the majority-carrier current. An inversion layer at the n-Si surface was also identified comprising a sheet carrier density greater than $8.6\times {10}^{11}$ cm${}^{-2}$ , and the MoO${}_x$ layer was found to be conductive though with a very high resistivity in the 10${}^4$ $\mathrm{\Omega }$ -cm range. We refer to these diodes as metal/non-insulator/semiconductor diodes and show with our device simulations that they can be mimicked as high-barrier Schottky diodes with an induced inversion layer at the interface.