Highly efficient silicon light emitting diodes produced by doping engineering

This paper reviews our recent progress on silicon (Si) pn junction light emitting diodes with locally doping engineered carrier potentials.Boron implanted Si diodes with dislocation loops have electrol...     

Noise in silicon double-base diodes

The power spectrum of the current fluctuations (noise) in the double-base diode has been measured experimentally and calculated theoretically. It has been found that there are two sources of noise in the double-base diode. First, there is the thermal noise of the real part of the ac admittance. The second source of noise is fluctuations in numbers of electrons and holes in the conduction band and valence band, respectively. Noise measurements are also presented for a diode with a long, high resistivity base region. These measurements are discussed qualitatively.     

Reciprocity in silicon Schottky-barrier diodes

Reciprocity has been examined at X band for low-noise silicon Schottky-barrier diodes by measuring the forward (r.f. to i.f.) and reverse (i.f. to r.f.) conversion losses by the heterodyne method. Reciprocity held for the silicon Schottky-barrier diodes, proving that their low conversion-loss behaviour is due to the nonlinear barrier resistance and not to parametric amplification caused by a nonlinear barrier capacitance. For comparison, silicon epitaxial point-contact and germanium point-contact diodes were also examined.     

LPVPE-grown silicon camel diodes

Low-pressure vapour-phase epitaxy (LPVPE) was applied to fabricate multilayer structures like camel diodes. Using in situ doping and selective growth, camel diodes with good ideality factors (1.08?1.2) and low generation-recombination currents were realised.     

X-band silicon TRAPATT diodes

Pulsed TRAPATT diodes have been successfully operated in X-band with 20 percent efficiency and 15 W output power. The diodes operate at the first subharmonic of the IMPATT frequency. Similar diodes have yielded 35 percent efficiency at 5.3 GHz as oscillators, and 54 percent efficiency at 3 GHz as RF triggered amplifiers.     

Silicon carbide blue-emitting diodes produced by liquid-phase epitaxy

Silicon carbide light-emitting diodes with emission in the blue range of the spectrum have been produced by two versions of the LPE process. Emission spectra and efficiency data are presented for diodes with different impurity levels. The highest external quantum efficiency observed so far at room temperature is 4 × 10^?5. The highest luminosity is 0.5 mcd at 100 mA, corresponding to a current density of 20 A/cm² and a beam of about one steradian. A brightness of 15 ftl/A/cm² is obtained.     

Tunneling recombination in silicon avalanche diodes

Distribution of the tunneling-recombination current over the space-charge region in a p-n junction was simulated mathematically. It is shown that the recombination rate saturates if the probability of tunneling is low. An expression for current-voltage characteristics of the p-n junction in the case of tunneling recombination is derived. The current-voltage characteristics of silicon avalanche diodes containing dislocations were studied experimentally. The results of numerical calculations based on the tunneling-recombination model are consistent with experimental data.     

Impact ionization in thin silicon diodes

We study the breakdown behavior of thin, abrupt silicon pin-diodes, using a low-power optical technique which can directly measure the avalanche multiplication factors even in the presence of large tunneling currents. Our measurements agree with a simple model for nonlocal avalanche generation, and we use this model to extend the breakdown predictions to a broad class of doped diodes similar to those found in the base-collector region of bipolar devices. Based on this analysis, we make quantitative estimates for the BV/sub CEO/ breakdown of modern Si and SiGe high-speed bipolar transistors.     

Temperature effects in silicon avalanche diodes

Gain-voltage curves for reach-through avalanche photodiodes are computed using the ionization rate data of van Overstraeten and de Man and Lee et al. and compared with measured curves. Noise spectral density measurements are also made and compared with McIntyre's avalanche noise theory. Agreement between computed and measured k-values as obtained from the noise measurements and between the computed and measured gain-voltage relationship can only be obtained with the ionization rate data of Lee et al. Gain-voltage curves were measured over the temperature range ?17 to +55°C and compared with computed curves in which temperature dependence of the ionization rate data of Lee et al. is computed using the modified Baraff theory. Excellent agreement between theory and experiment is obtained.     

Liquid-nitrogen-cooled submillimetre-wave silicon IMPATT diodes

400 and 300 GHz c.w. oscillation characteristics for liquid-nitrogcn-cooled silicon IMPATT diodes are described. Output powers of 2.2 and 4.5 mW have been obtained at 412 and 295 GHz, respectively, and a highest oscillation frequency of 430 GHz observed.     

Passivated millimeter-wave silicon IMPATT diodes fabricated by ion implantation

Ion implantation has been combined with planar-mesa processing techniques to realize a passivated silicon IMPATT diode for millimeter-wavelength operation. A continuous-wave output power of 100 mW was obtained at 62 GHz from a fully passivated single-drift-region p⁺-n-n⁺structure.     

Noise in epitaxial silicon bulk unipolar diodes

Silicon camel diodes with barrier heights in the range 0.46?0.94 eV were realised by means of low-pressure vapour phase epitaxy (LPVPE). These diodes show a conversion loss as low as 4.2 dB at 2 GHz and a noise figure of 4.8 dB.     

Electron drift velocity in avalanching silicon diodes

The differential resistance of an avalanching p⁺nn⁺junction is used to obtain the electron drift velocity at electric fields where significant avalanching is occurring (2 × 10⁵< E < 4 × 10⁵V/cm). The velocity is also obtained as a function of temperature and is consistent with energetic phonon scattering.     

Shot noise in silicon Schottky barrier diodes

Noise measurements have been performed on forward and reverse-biased silicon Schottky barrier diodes. Measurements were performed in the frequency range of 100 Hz to 50 kHz. Apart from excess noise observed for some diodes in a portion of this frequency range, the noise for the diodes was found to be in excellent agreement with shot-noise theory. Some refinements of the shot-noise theory have been considered, but the difference between the refined and the simple theories was not resolvable in our measurements. A useful noise-measurement technique is described.     

Modes of avalanche oscillations in silicon diodes

A computer program which includes both electronic and thermal processes has been used to study avalanche oscillations in a diode which is punched through only well above breakdown. IMPATT, relaxing avalanche, and MULTIPATT oscillations have been studied. The MULTIPATT mode is shown to be a superpesition of transit-time oscillations upon a relaxation oscillation. It is postulated that the TRAPATT mode is initiated by the IMPATI mode via the MULTIPATI mode. The frequency of the IMPATT oscillations was found to vary with the square root of the current over a factor of 100 in current. For parallel operation of TRAPATT diodes, it is shown that nonpunched-through diodes should be used.     

Hydrogen-sensitive silicon tunnel MIS switching diodes

Palladium thin SiO2-n-p⁺silicon switching diodes have been fabricated in which the turn-on voltage changes in proportion to the hydrogen concentration in the ambient gas. In the typical diode operated at 100°C, the switching voltage decreases from 5.1 to 3.6 V for 10 ppm hydrogen in air within 2 min and the off-state disappears for 100 ppm within 30 s. Hydrogen sensitivity is ascribed to the increase of a current gain in two transistor model of the device due to the change in palladium work-function.     

Computer calculation of silicon avalanche diodes

The efficiency η and output power P per unit area were computed for silicon p-n-n⁺avalanche diodes having an active region of 5 microns. The condition for making both η andPmaximum is that the field at the n-n⁺interface generated by impurity and bias voltage is about one fourth of that at the junction under oscillation conditions. The maximum η andPwere calculated to be about 20.5 per cent and 53 kW/cm². Dc current density J0for maximumPwas about 4200 A/cm². On the other hand, J0for maximum η was calculated to be about 800 A/cm². It was found that a diode having an abrupt type junction is the best. The condition under which a diode is represented by use of a diode with abrupt type junction is that the region of a homogeneous field near the junction is less than one fifth of the space-charge region.     

Heat treatments of gold-doped silicon diodes

Gold-doped p⁺-n silicon diodes were subjected to heat treatments in the 700°-850°C range, and changes in the diode recovery time as a function of heat-treat time were noted. The recovery time was observed to increase with heat-treat time in two stages. In the first stage, the recovery time trincreases typically by a factor of 30 in several hours of annealing. In the second stage, which covers an additional 120 hours of annealing, the data points are more scattered, ranging from no increase in trto an increase by a factor of 10. Between the two stages trdecreases for a brief period. The data for the first stage fit the interpretation that the gold ceases to function as a recombination center when it jumps from a substitutional site to a nearby interstice. Using this interpretation, the time constant for the process is τ=10^-3exp (1.36 eV/kT) seconds. The second stage of annealing is tentatively explained by the annealing of another group of recombination centers. These may be due to interactions of the gold dissociation reaction products among themselves or with other impurities.     

RF Sputtered gold-amorphous silicon Schottky-barrier diodes

Gold Schottky-barrier diodes formed on reactively sputtered amorphous silicon thin films have been investigated. Device forwardI-Vcharacteristics are well modeled as a Schottky diode in series with a temperature activated series resistor. At 300K, the forward current indicates a diode correction factor of 1.4 and a saturation current of 5.8 × 10^-10A/cm². The metal-semiconductor barrier height is 0.93 eV. Capacitance versus frequency measurements indicate a depletion region thickness of 3000 Å. In the depletion region, the mobility-lifetime products are estimated to be of the order of 5 × 10^-11cm²/V which is substantially less than the value of 10^-7cm²/V in the quasi-neutral region, It is suggested that deep gap states are responsible for this difference. Carrier recombination in the depletion region limits the photovoltaic performance.