Erbium ion electroluminescence in p ++/n +/n-Si:Er/n ++ silicon diode structures

Results of experimental studies of erbium ion electroluminescence in p ⁺⁺/n ⁺/n-Si:Er/n ⁺⁺ silicon diode structures grown by sublimation molecular-beam epitaxy are discussed. The distinctive feature of these structures is that the regions of electron flux formation of (n ⁺-Si) and impact excitation of erbium ions (n-Si:Er) are spaced. The influence of the n ⁺-Si layer thickness on electrical and electroluminescent properties of diodes was studied. It was shown that n ⁺-Si layer thinning causes the transformation of the structure breakdown mechanism from tunneling to avalanche. The dependence of the Er³⁺ ion electroluminescence on the thickness of the heavily doped n ⁺-Si region is bell-shaped. At the n ⁺-Si-layer doping level n ≈ 2 × 10¹⁸ cm^?3, the maximum electroluminescence intensity is attained at an n ⁺-Si layer thickness of ～23 nm.     

Electroluminescence properties of LEDs based on electron-irradiated <Emphasis Type="Italic">p</Emphasis>-Si

The electroluminescence (EL) in n⁺–p–p⁺ light-emitting-diode (LED) structures based on Si irradiated with electrons and annealed at high temperature is studied. The LEDs are fabricated by the chemical- vapor deposition of polycrystalline silicon layers doped with high concentrations of boron and phosphorus. Transformation of the EL spectra with current in the LEDs is well described by six Gaussian curves. The peak positions of these curves are current-independent and equal to 1233, 1308, 1363, 1425, 1479, and 1520 nm. The dependences of the integrated EL intensity and of the full-width at half-maximum (FWHM) of the lines on current are examined.     

Voltage dependence of the differential capacitance of a p +-n junction

The dependences of the differential capacitance and current of a p ⁺-n junction with a uniformly doped n region on the voltage in the junction region are calculated. The p ⁺-n junction capacitance controls the charge change in the junction region taking into account a change in the electric field of the quasi-neutral n region and a change in its bipolar drift mobility with increasing excess charge-carrier concentration. It is shown that the change in the sign of the p ⁺-n junction capacitance with increasing injection level is caused by a decrease in the bipolar drift mobility as the electron-hole pair concentration in the n region increases. It is shown that the p ⁺-n junction capacitance decreases with increasing reverse voltage and tends to a constant positive value.     

Features of the electroluminescence spectra of quantum-confined silicon p +-n heterojunctions in the infrared spectral region

The results of studying the characteristics of optical emission in various regions of quantum-confined silicon p ⁺-n heterojunctions heavily doped with boron are analyzed. The results obtained allow one to conclude that near-infrared electroluminescence arises near the heterointerface between the nanostructured wide-gap silicon p ⁺-barrier heavily doped with boron and n-type silicon (100), the formation of which included the active involvement of boron dipole centers.     

Effect of neutron irradiation on the structure of silicon p-n junctions of voltage limiters

Changes in capacitance-voltage characteristics of p-n junctions with a linear or close-to-linear uncompensated charge distribution under neutron irradiation are analyzed. It is confirmed that an intrinsic conductivity region is formed near the p-n junction due to such exposure. Empirical formulas are derived which describe the dependence of the sizes of this region and the effective concentration gradient of uncompensated charge on the neutron fluence in a wide range of initial (before neutron irradiation) concentration gradients (from 3 × 10¹⁸ to 2 × 10²⁰ cm^?4) and initial silicon resistivities (from 0.3 to 2 Ω cm).     

Injection-induced terahertz electroluminescence from silicon <Emphasis Type="Italic">p–n</Emphasis> structures

Injection-induced terahertz electroluminescence from silicon p ⁺–n structures is observed at helium temperatures. Structures fabricated by the diffusion of boron into a phosphorus-doped n-Si substrate are studied. Relatively narrow luminescence lines are observed in the luminescence spectra against a broad smooth background. The spectral position of a number of emission lines corresponds to optical transitions between excited donor states and the ground state of phosphorus donors. The intracenter optical transitions of electrons at phosphorus donors are excited as a result of recombination processes occurring in the n-type region of the structure under the injection of nonequilibrium holes. A number of other lines in the terahertz emission spectra are associated with intracenter transitions at acceptor centers, which are also excited as a result of injection. The structureless background in the electroluminescence spectra may be due to terahertz emission upon the intraband energy relaxation of “hot” carriers having an effective temperature exceeding the lattice temperature. These “hot” carriers appear in the structure under injection conditions.     

Dynamic minority-carrier storage in TRAPATT diodes

The occurrence of a dynamic storage of minority carriers in the highly-doped boundary regions of a TRAPATT diode and the subsequent release of these carriers into the diode's depletion region is verified for the first time in detailed computer simulations of the diode's internal dynamics. The simulations were carried out by numerical solution of the carrier transport equations in a p⁺?n?n⁺ silicon diode having a deep-diffused doping profile typical of experimental devices. The results show that it is this storage process, and not thermal generation, that controls the carrier avalanche even in very gradually graded structures. The dynamics of this phenomenon are described in detail and the implications of the results on TRAPATT oscillator performance are discussed.     

Effect of the fabrication conditions of SiGe LEDs on their luminescence and electrical properties

SiGe-based n⁺–p–p⁺ light-emitting diodes (LEDs) with heavily doped layers fabricated by the diffusion (of boron and phosphorus) and CVD (chemical-vapor deposition of polycrystalline silicon layers doped with boron and phosphorus) techniques are studied. The electroluminescence spectra of both kinds of LEDs are identical, but the emission intensity of CVD diodes is ～20 times lower. The reverse and forward currents in the CVD diodes are substantially higher than those in diffusion-grown diodes. The poorer luminescence and electrical properties of the CVD diodes are due to the formation of defects at the interface between the emitter and base layers.     

<Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript>-Si-<Emphasis Type="Italic">n</Emphasis>-CdF<Subscript>2</Subscript> heterojunctions

Boron diffusion and the vapor-phase deposition of silicon layers are used to prepare ultrashallow p⁺-n junctions and p⁺-Si-n-CdF₂ heterostructures on an n-CdF₂ crystal surface. Forward portions of the I–V characteristics of the p⁺-n junctions and p⁺-Si-n-CdF₂ heterojunctions reveal the CdF₂ band gap (7.8 eV), as well as allow the identification of the valence-band structure of cadmium fluoride crystals. Under conditions in which forward bias is applied to the p⁺-Si-n-CdF₂ heterojunctions, electroluminescence spectra are measured for the first time in the visible spectral region.     

Edge electroluminescence of the effective silicon point-junction light-emitting diode in the temperature range 80–300 K

The edge electroluminescence spectra of silicon point-junction light-emitting diodes with a p-n junction area of 0.008 mm² are studied at temperatures ranging from 80 to 300 K. Unprecedentedly high stability of the position of the spectral peak is observed at temperatures in the range between 130 and 300 K. The spectral characteristics of the light emitting diodes are studied at 80 K at different current densities up to 25 kA/cm². In contrast to the earlier reported data obtained at 300 K, the data obtained at 80 K do not show any noticeable Augerrecombination-related decrease in the quantum efficiency. From an analysis of the electroluminescence spectra at 80 K in a wide range of currents, it follows that radiative annihilation of free excitons is not a governing mechanism of electroluminescence in the entire emitting region in the base of the point-junction light-emitting diode at all currents used in the experiment.     

Impact ionization of excitons in single-crystal silicon and its effect on the exciton concentration and luminescence near the fundamental absorption edge

The effect of impact ionization of excitons by free charge carriers on the exciton concentration in single-crystal silicon (c-Si) at room temperature and at a high injection level is investigated. At sufficiently high concentrations of free electrons (n), the impact ionization dominates over thermal ionization. At such n, the effect results in much lower exciton concentrations (n _ex) compared to those with disregard of it and linear or almost linear portions in the dependences n _ex(n) and the dependences of the near-band-edge luminescence intensity in c-Si on the intensity of its excitation. The proposed technique for calculating n _ex can be developed for other semiconductors at other temperatures.     

Effects of time dependence of multiplication process on avalanche noise

Theoretical and experimental studies of noise generated due to the randomness of the multiplication process in the avalanche region of a uniform diode are presented. The theory extends the results of McIntyre to include the time dependence of the multiplication process. It also shows the correspondence between the results of McIntyre, Gummel and Blue, Hines and Tager. The space-charge feedback and transit-time effects have been neglected in this analysis. The theoretical and the experimental results described have shown that even at frequencies well below transit-time frequency, the importance of the factor resulting from consideration of the time dependence of the multiplication process cannot be ignored.The measurements of the avalanche noise on uniform p⁺-n-n⁺ silicon diodes are found to be in good agreement with the theory presented here.     

Application of the transmission line equivalent circuit model to the analysis of the PN junction admittance under d.c. bias

Exact non-equilibrium one-energy-level numerical solutions of the admittance of a p+n junction are obtained from the nonuniform transmission line equivalent circuit model. Capacitance and conductance curves for equilibrium and reverse-biased gold-doped silicon diode are calculated using experimental values of emission and capture rates. Comparisons between theoretical and experimental frequency dependences of the admittance using new experimental capture rates show good agreements over a wide range of reverse bias.     

Small-signal analysis of punch-through injection microwave devices

A theoretical small-signal analysis of punch-through injection microwave devices is given. A numerical study of a silicon p⁺?n?p⁺ structure is performed, which shows good agreement with experimental measurements by Snapp and Weissglas for a diode with a doping density of 1·2 × 10¹⁵/cm³. Negative resistance is also calculated for diodes with doping densities of 0·6 × 10¹⁵/cm³ and 5 × 10¹⁵/cm³. A partially analytical mode, including the lowfield region, is developed and compared with the numerical calculation. Ohmic losses for devices with low impurity concentrations and diffusion for devices with high impurity concentrations are shown to be significant factors.The noise spectrum is calculated numerically from the assumption of two noise sources, injection noise and diffusion noise. The noise measure is determined and shown to be in good agreement with experiments by Björkman and Snapp.     

Electroluminescence at a wavelength of 1.54 μm in Si:Er/Si structures consisting of a number of <Emphasis Type="Italic">p-n</Emphasis> junctions

A method of connecting several p ⁺-n junctions in the same Si:Er/Si structure is demonstrated; this method makes it possible to increase the electroluminescence intensity at a wavelength of 1.54 μm. The structures have been grown by sublimation molecular-beam epitaxy.     

Self-Action of Intense Millimeter Waves in Waveguides with Integrated P-I-N Structures

The nonlinear interaction of high power millimeter (mm) electromagnetic waves with silicon integral p-i-n structures placed in a metal waveguide is theoretically investigated. The level of double injection of charge carriers due to detection of high intensity millimeter wave electric field in p-i-n structures is estimated. A mathematical model of the mutual influence of electromagnetic waves and injected charge carriers in the active region of p-i-n structures is formulated. A numerical solution of the nonlinear Helmholtz equation supplemented by proper boundary conditions on the active region boundary is obtained. The effect of high-power electromagnetic waves leads to an excessive injection of carriers into the active region of the semiconductor between p⁺-i, n⁺-i injection junctions and redistribution of the electric field in the structure. The reflection and transmission coefficients vary rapidly with the change in the input amplitude of the electromagnetic wave. This leads to bistability of these coefficients. The bistability is more pronounced in the low-frequency part of the mm range.     

Profiling the boron distribution in asymmetric n +-p silicon photodiodes and a new concept for creating selectively sensitive photocells for megapixel color-image receivers

The spectral photosensitivity of n ⁺-p silicon photodiodes with a p ⁺ layer implanted in the substrate is studied experimentally. It is demonstrated that such p ⁺ doping effectively shifts the long-wavelength edge of the photosensitivity in the optical spectral range and the shift depends on the depth of the p ⁺ layer. A new concept for creating selectively sensitive photocells for megapixel color-image receivers is proposed. The receivers are based on n ⁺-p photodiode structures containing a few layers that are implanted at different depths and form desired color-separating potential barriers and lateral diffusion channels for collection of the minority carriers generated by photons of different colors.     

Electroluminescence at 1.54 μm in Si:Er/Si structures grown by sublimation molecular-beam epitaxy

In Si:Er/Si diode structures grown by sublimation molecular-beam epitaxy in a vacuum with a pressure of ～10^?7 mbar at temperatures 520–580°C, the intensity of room-temperature electroluminescence at 1.54 μm is studied as a function of the concentration and distribution of erbium and donor impurities in the space-charge region (SCR) and the SCR width. Methods for obtaining electroluminescence in diodes with a wide (0.1–1 μm) SCR are developed. The mean free path of electrons with respect to their interaction with Er centers and the threshold energy a free electron needs in order to excite an Er-shell electron are determined. The values of electric-field strength corresponding to breakdown in silicon p-i-n diodes with and without Er doping are obtained experimentally. A model describing the interaction of hot electrons with Er centers is suggested.     

Spectral response of an injection-mode infrared detector

Large injection pulses are observed in simple circuits containing forward-biased silicon p-i-n (p⁺-n-n⁺) structures at liquid helium temperatures. The pulse rate is dependent on the intensity of infrared radiation incident on the device. The substantial voltage, current, and power output eliminates the need for on-chip or off-chip amplifiers. The first observation of the spectral response of such a detector as measured from 22 to 32 μm with a liquid-helium-cooled monochromator is reported. The response is similar to other extrinsic detectors and modulated by a multiple internal reflection interference pattern. The interference pattern and the origin of optical absorption are analyzed.     

Impedance and barrier capacitance of silicon diodes implanted with high-energy Xe ions

Characteristics of Si p⁺n diodes with non-uniformly distributed compensating defects, which were introduced by implantation with Xe²³⁺ ions, have been studied. The layer with the maximum concentration of the compensating defects was located in the vicinity of the metallurgical p-n junction. It is found that the presence of the defect layer results in non-monotonic dependences of the imaginary part of impedance (−Z″) and differential conductance (G = −dI/dU) of the implanted diodes on reverse bias voltage U. An equivalent circuit of the irradiated diode is proposed, which allows us to approximate the measured frequency dependences of capacitance and conductance of the irradiated diodes and to determine values of diode barrier capacitance C_pn at different reverse bias voltages.