Abstract:This work presents a monolithic laterally-coupled wide-spectrum (350 nm < λ < 1270 nm) optical link in a silicon-on-insulator CMOS technology. The link consists of a silicon (Si) light-emitting diode (LED) as the optical source and a Si photodiode (PD) as the detector; both realized by vertical abrupt n + p junctions, separated by a shallow trench isolation composed of silicon dioxide. Medium trench isolation around the devices along with the buried oxide layer provides galvanic isolation. Optical coupling in both avalanche-mode and forward-mode operation of the LED are analyzed for various designs and bias conditions. From both DC and pulsed transient measurements, it is further shown that heating in the avalanche-mode LED leads to a slow thermal coupling to the PD with time constants in the ms range. An integrated heat sink in the same technology leads to a ∼ 6 times reduction in the change in PD junction temperature per unit electrical power dissipated in the avalanche-mode LED. The analysis paves way for wide-spectrum optical links integrated in smart power technologies.

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 (&gt;105 V/cm). The photon emission rate is described as a function of the electron temperature Te, which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range (λ∼ 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 (∼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.

This article describes novel composite thin films consisting of GaN, C, and Ga (termed “GaCN”, as an analogue to BCN and other carbonitrides) as a prospective material for future optical applications. This is due to their tunable refractive index that depends on the carbon content. The composites are prepared by introducing alternating pulses of trimethylgallium (TMG) and ammonia (NH3) on silicon substrates to mimic an atomic layer deposition process. Because the GaCN material is hardly reported to the best of our knowledge, a comprehensive characterization is performed to investigate into its chemical nature, primarily to determine whether or not it exists as a single-phase material. It is revealed that GaCN is a composite, consisting of phase-segregated, nanoscale clusters of wurtzitic GaN polycrystals, in addition to inclusions of carbon, nitrogen, and gallium, which are chemically bonded into several forms, but not belonging to the GaN crystals itself. By varying the deposition temperature between 400 and 600 °C and the NH3 partial pressure between 0.7 × 10–3 and 7.25 mbar, layers with a wide compositional range of Ga, C, and N are prepared. The role of carbon on the GaCN optical properties is significant: an increase of the refractive index from 2.19 at 1500 nm (for carbon-free polycrystalline GaN) to 2.46 (for GaCN) is achieved by merely 10 at. % of carbon addition. The presence of sp2-hybridized C=N clusters and carbon at the interface of the GaN polycrystals are proposed to determine their optical properties. Furthermore, the formation of the GaN polycrystals in the composite occurs through a TMG:NH3 surface-adduct assisted pathway, whereas the inclusions of carbon, nitrogen, and gallium are formed by the thermal decomposition of the chemisorbed TMG species.

A silicon-on-insulator based optical link is introduced. Higher opto-coupling efficiency and temperature-resilience are obtained via avalanche-mode light-emitting diode operation against forward-mode operation. Self-heating induced thermo-coupling in steadystate is de-embedded by calibrating the photo-detector's photovoltaic characteristics.

In this paper, we investigate the presence of minority carriers and their role in charge carrier transport in silicon (Si) Schottky diodes with a high potential barrier. Using TCAD simulations along with an analytical model, we show that an inversion charge is induced at the metal-semiconductor (MS) interface in a high-barrier Schottky diode which imparts bipolar-type current characteristics to otherwise a unipolar Schottky diode, even at low-injection operation. In such a high-barrier diode, minority diffusion also becomes important along with the majority carrier thermionic emission and therefore cannot be neglected, unlike in a conventional Schottky diode. The presence of minority carriers at low injection in a high-barrier Si Schottky diode has been experimentally verified via a prior-reported two-diode electrical test method, reverse recovery measurements, and by measuring infrared electroluminescence. It is also shown, via TCAD simulations, that the diffusion component becomes more pronounced in case of a reduced Gummel number and at elevated temperatures.