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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 × 10 11 cm − 2 , and the MoO x layer was found to be conductive though with a very high resistivity in the 10 4 Ω -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. [ABSTRACT FROM AUTHOR]

In this paper, we study the switching behavior of silicon-on-insulator light-emitting diodes (LEDs). Through the comparison of various device geometries, we establish the dimensional dependence of the switching speed of the LED. TCAD simulations are in line with the experimental results. Our findings indicate that ON–OFF keying up to GHz frequencies should be feasible with such diodes, although a design optimized for higher frequency operation will exhibit a reduced light emission efficiency. [ABSTRACT FROM AUTHOR]

We report on the dependency of the optical power efficiency \eta on the breakdown voltage {V}_{\text {BR}} of avalanche-mode (AM) light-emitting diodes (LEDs) in silicon. Lateral p+-n-n+ LEDs have been designed in a 65-nm bulk CMOS technology, where {V}_{\text {BR}} is varied between 2 and 9 V. This tunes both the magnitude and the spatial distribution of the reverse electric field, which governs AM electroluminescence. Experiments show that a maximum \eta of \sim 1.7 \times 10^{-6} is obtained for {V}_{\text {BR}} \sim 6 V. For V\text {BR} < 6 V, non-local avalanche results in a lower \eta , while for V\text {BR} > 6 V, a gradual reduction in \eta with increasing {V}_{\text {BR}} is obtained. This trend is compared with two recently proposed opto-electronic models. A maximum in \eta $ at relatively low voltages is attractive for monolithic opto-electronic integration in silicon [ABSTRACT FROM AUTHOR]

Avalanche-mode light-emitting diodes (AMLEDs) in silicon (Si) are potential light sources to enable monolithic optical links in standard CMOS technology, due to the large overlap of their electroluminescent (EL) spectra with the responsivity of Si photodiodes. These EL spectra depend on the reverse electric field. We present AMLEDs employing the superjunction (SJ) assisted reduced surface-field (RESURF) effect, which increases the uniformity of their electric field profile. Consequently, the EL area of these lateral devices is significantly enlarged as compared with conventional AMLEDs. Electrical and opticalmeasurements demonstrate RESURF, as predicted by TCAD simulations, and show a direct link between EL-intensity (optical power per unit device area) and the field profile. Contrary to a conventional AMLED, the breakdown voltage of the avalanche-mode SJ-LED scales with the device length. Furthermore, the brightest SJ-LED, with a lateral intensity of ~30 mW cm−2 at an electrical power ( P\textrm {AMLED} ) of 0.1W, shows a twofold higher internal quantum efficiency and a threefold higher EL-intensity compared with the conventional AMLED for the same P\textrm {AMLED} . This particular SJ-LED also shows an optimum radiative recombination efficiency at a current density of around ~800 A cm−2. [ABSTRACT FROM PUBLISHER]

A simple analytical model for p-i-n light-emitting diodes is presented to give insight into the device physics. The 1-D model describes the dc electrical characteristics and internal quantum efficiency (\etaIQE) as a function of the applied bias and is in good agreement with TCAD simulations. An optimization scheme, based on the same model, shows improved \etaIQE for engineered heterojunctions by reducing the diffusion current contribution. The results show that the use of heterojunctions increases the light intensity inside a narrow-bandgap material, akin to the experimentally observed results. The bandgap of the active region determines the voltage at which the maximum efficiency occurs. It is also shown that maximum \etaIQE occurs at a lower bias than that typically used for studying the maximum light intensity. The effect of injection dependence of recombination coefficients on the efficiency is also studied. For the first time, the electrical performance of a multilayer active region is modeled. [ABSTRACT FROM PUBLISHER]