The observation of electroluminescence in a double barrier resonant tunnelling structure

Electroluminescence (EL) and impact ionisation phenomena in an asymmetric double barrier resonant tunnelling structure are investigated. Determination of the charge density and electric field distribution throughout the structure enables a detailed analysis of impact ionisation phenomena to be made.     

Impact ionization and electroluminescence in single barrier tunnelling structures

At high electric fields, hot electrons injected into the undoped regions of n-i-n structures can give rise to impact ionization of the host lattice and electron-hole pair production. The holes created by impact ionization recombine with majority carrier electrons, leading to electroluminescence (EL) from the device at fields in excess of 10⁵V/cm. In the present work, we show that the study of such EL in GaAs/AlGaAs/GaAs single barrier tunnelling structures provides a simple and effective quantitative method to determine impact ionization coefficients in GaAs. Structures with undoped regions of length 100, 150 and 200nm are shown to give very similar results for the impact ionization coefficient. The values obtained for the impact ionization coefficient are shown to be consistent with those obtained by carrier multiplication methods.     

ZnO纳米线双绝缘层结构电致发光器件制备及特性研究

在利用液相法生长ZnO纳米线薄膜的基础上，构造成功基于ZnO纳米线双绝缘层结构的交流电致发光器件.此器件呈现出良好的阻容特性，在室温下以一定频率的交流电压驱动，可观察到近紫外波段387 nm处和可见光波段552 nm处的发射谱带.从阻容结构的导电特性及ZnO纳米线材料的能带结构等方面探讨了这种器件的电致发光机理及频率特性.     

Confinement in a double barrier structure in the presence of an electric field

The effect of an electric field on the electron resonant tunnelling into a double barrier structure is studied. We show for particular field strengths an increase of the tunnelling time which helps us to explain the Stark-ladder localization and to discuss Bloch oscillations and the quenching of luminescence in multiple quantum wells.     

Electron-phonon scattering in an asymmetric double barrier resonant tunneling structure

We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy. The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable to the dwell time of electrons in the quantum well for a typical resonant tunneling structure. Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998     

Short-wave infrared detector with double barrier structure and low dark current density

Short-wave infrared(SWIR) detectors combining AlAs∕In_(0.53)Ga_(0.47) As∕AlAs double barrier structure(DBS)with In_(0.53)Ga_(0.47) As absorption layer are fabricated by molecular beam epitaxy.By adding a p-charge layer,the dark current density of the detector is lowered by 3 orders of magnitude.The responsivity of the detector is tested at room temperature,which reaches 6000 A/W when the power of the incident light is 0.7 nW.The noise equivalent power(NEP) of the detector at 5 kHz is measured to be 3.77 × 10~(-14) W∕Hz~(1∕2) at room temperature.     

Nonlinear transport of Bose--Einstein condensates in a double barrier potential

The stable nonlinear transport of the Bose-Einstein condensates through a double barrier potential in a waveguide is studied. By using the direct perturbation method we have obtained a perturbed solution of Cross-Pitaevskii equation. Theoretical analysis reveals that this perturbed solution is a stable periodic solution, which shows that the transport of Bose-Einstein condensed atoms in this system is a stable nonlinear transport. The corresponding numerical results are in good agreement with the theoretical analytical results.     

Photocurrent response in a double barrier structure with quantum dots–quantum well inserted in central well

We report the photocurrent response in a double barrier structure with quantum dots–quantum well inserted in central well. When this quantum dots–quantum well hybrid heterostructure is biased beyond +1 or −1 V, the photocurrent response manifests itself as a step-like enhancement, increasing linearly with the light intensity. Most probably, at proper bias condition, the pulling down of the X minimum of GaAs at the outgoing interface of the emitter barrier by the photovoltaic effect in GaAs QW will initiate the Γ–X–X tunneling at much lower bias as compared with that in the dark. That gives rise to the observed photocurrent response.     

Infrared electroluminescence from a Si MOS structure with Ge in the oxide

We report on room-temperature infrared electroluminescence (EL) from metal-oxide-semiconductor devices made from Si. We compare the luminescence from RF sputtered oxide films containing SiO₂ with and without Ge by using a composite target and luminescence from a SiO₂ layer made by rapid thermal oxidation. The sputtered films were annealed in the temperature range 600-900 °C. This densifies the films and is likely to reduce the concentration of defects. A luminescence peak located around 1150-1170 nm is observed at current densities as low as 0.1 A/cm². The corresponding photon energy is close to that of the Si band gap. In addition, we observe several broad luminescence bands in the range 1000-1750 nm. These bands get stronger with Ge in the SiO₂ film. Some of these bands have previously been suggested and are directly associated with Ge. Since we observe that the intensity is correlated with the presence of Ge while the mere presence of the bands is not, we discuss the EL bands being due to defects which concentration is influenced by Ge in the oxide.     

Spin-polarized current produced by a double barrier resonant tunneling diode

The spin-polarized tunneling current through a double barrier resonant tunneling diode (RTD) made with a semimagnetic semiconductor is studied theoretically. The calculated spin-polarized current and polarization degree are in agreement with recent experimental results. It is predicted that the polarization degree can be modulated continuously from +1 to −1 by changing the external voltage such that the quasi-confined spin-up and spin-down energy levels shift downwards from the Fermi level to the bottom of the conduction band. The RTD with low potential barrier or the tunneling through the second quasi-confined state produces larger spin-polarized current. Furthermore a higher magnetic field enhances the polarization degree of the tunneling current.     

Self-oscillating mixing in a QW double barrier diode at W-band

We report the presence of self-oscillating mixing in an asymmetric quantum well double barrier diode at 86GHz. We have demonstrated that the QW device can be injection-locked to the RF signal, and that the intermediate frequency (IF) can exhibit both upper and sub harmonics. Conversion gain was measured and found to be typically –30 to –40dB, with a best measurement of –18.79dB. Under certain conditions, the IF could show wideband chaotic-like oscillations extending to 1500Mhz.     

Wigner function study of a double quantum barrier resonant tunnelling diode

Resonant tunnelling structures are receiving attention as a testbed for theoretical approaches to quantum transport. We present a Wigner function study of a double quantum barrier resonant tunnelling device formed by layers of AlGaAs in GaAs. Our study deals with the influence of the boundary conditions on the initial distribution as well as on the time-evolution of the system. We use a Gaussian wave packet to study the numerical effects of the boundaries. We attempt to solve the system in both the time-evolution and steady-state cases, including self-consistency in the potential.     

The I-V characteristics of double barrier stair-wells

We investigated the I-V characteristics of the double barrier stair-well structure. Resonant tunneling current is achieved by application of an electric field, which increases the transmission under positive bias and decreases it under the reverse bias. This asymmetry can be used for rectification and the device works as a quantum diode. Furthermore, the same structure can perform, under negative bias, resonant tunneling processes with different characteristics.     

Relation between crystal structure and electroluminescence in ZnS-Mn crystals

The electroluminescence of ZnS-Mn crystals annealed in zinc melt is investigated. When an external field of 10³-10⁴ V/cm is applied, continuous radiation is emitted over the whole volume of the spcimen. The volt-brightness characteristics are approximated by various functions and depend on the conditions of excitation. The results obtained are explained by the concentration of the electric field at barrier formed by partial dislocations at the place where they cut the hexagonal layers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 33–37, September. 1985.     

Ordering of crystal structure by ionizing radiation

We have studied the action of ionizing radiation on defect-containing semiconductor crystals, metals, and alloys. Using modern methods for investigation of solids, Rutherford back scattering of channeled charged particles, x-ray diffraction, electron microscopy, and also calorimetric methods, we have established: a) irradiation (by x-ray beams, gamma rays, and electrons) of metals and alloys with an equivalent radiation dose less than 10⁵ J/kg and of semiconductor crystals with a dose less than 10³ J/kg does not lead to additional accumulation of defects but conversely leads to elimination of defects and transition of the crystal to a more equilibrium state; b) ionization processes play a determining role in rearrangment of defects in crystals exhibiting both semiconductor and metallic conductivity. We show that rearrangment of the crystal occurs as a result of stored energy in the crystal which is liberated due to chain reactions of annihilation of defects, initiated by ionization. Transition of the crystal to the equilibrium state is accompanied by improvement of its physical properties.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 58–67, December, 1994.