Semiconductor Plasma Research Articles

Electron–hole two-stream instability in a quantum semiconductor plasma with exchange-correlation effects

The electron–hole two-stream instability in a quantum semiconductor plasma has been studied including electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures of the plasma species. Typical values of GaAs and GaSb semiconductors are used to estimate the growth rate of the two-stream instability. The effects of electron– and hole–phonon collision, quantum recoil effects, the streaming velocities, and the corresponding threshold on the growth rate are investigated numerically. Considering the phonon susceptibility allows the acoustic mode to exist and the collisional instability arises in combination with drift of the holes.

Polaron induced parametric interactions in magnetized semiconductors

In the framework of hydrodynamic model of semiconductor plasma, the parametric amplification due to polaron mode has been analytically investigated in a magnetized III–V semiconductor, viz. n-InSb. The origin of the phenomenon lies in the effective second-order optical susceptibility arising due to the induced nonlinear current density of the medium. Using the coupled-mode theory, the expressions for the parametric gain coefficient and the threshold amplitudes of the external electric field above which the parametric instability can occur are derived. The effect of the wave vector and the strength of the external magnetic field on the gain coefficient and the threshold amplitude of the pump electric field are analyzed. Reported results strongly suggest that at appropriate pump electric field, proper selection of the magnetic field not only lowers threshold pump field required for the onset of parametric excitation but also enhances gain effectively.

Optical phase conjugation reflectivity via stimulated Brillouin scattering in acousto-optic diffusive semiconductor plasma crystal

Analytical investigation has been made for optical phase conjugation (OPC) reflectivity via stimulated Brillouin scattering (SBS) in acousto-optic diffusive semiconductor plasma crystal. Our analysis is based on hydrodynamic model and coupled mode approach of interacting waves. The numerical estimations are made for n-type InSb semiconductor plasma crystal duly irradiated by CO2 laser. The magnitude of the third-order nonlinear optical susceptibility for III-V semiconductor obtained from our analysis is found to agree well with the experimental values. Maximum OPC reflectivity is obtained when cyclotron frequency is in resonance with applied pump frequency.

Optically controlled terahertz beam steering and imaging

We propose a spatial modulator for terahertz waves based on light induced electron plasma in photo-active semiconductors. A two-dimensional array of computer controlled light is used to create free carries in bulk silicon, which results in a spatial modulation of the transmission at terahertz frequencies. This method not only exhibits a remarkable modulation depth over a broad frequency range but also allows for an optically controlled beam steering of terahertz waves by inducing virtual grating structures. In addition, we analyze the possibility of all-optically controlled terahertz imaging.

Asymptotic stability of stationary solutions to the drift-diffusion model in the whole space

We study the initial value problem for the drift-diffusion model arising in semiconductor device simulation and plasma physics. We show that the corresponding stationary problem in the whole space ℝn admits a unique stationary solution in a general situation. Moreover, it is proved that when n ≥ 3, a unique solution to the initial value problem exists globally in time and converges to the corresponding stationary solution as time tends to infinity, provided that the amplitude of the stationary solution and the initial perturbation are suitably small. Also, we show the sharp decay estimate for the perturbation. The stability proof is based on the time weighted L p energy method.

Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

Amplitude modulation and demodulation of an electromagnetic wave in magnetised acousto-optic diffusive semiconductor plasmas: Hot carrier effects

In communication processes, amplitude modulation is very helpful to save power using a single band transmission. Using the hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave incorporating carrier heating (CH) effects in acousto-optic magnetised semiconductor plasma. The CH effects add new dimensions in the present analysis. Analysis are made under different wave number regions over a wide range of cyclotron frequencies. It is found that incorporation of CH effects modifies the amplitude modulation and demodulation processes effectively. Numerical estimations are made for III–V semiconductor crystal irradiated by pump wave of frequency 1.6×10 13 s −1. Complete absorption of the waves takes place in all the possible wavelength regimes when the cyclotron frequency ω c becomes nearly equal to ω 0, the pump frequency on neglecting the collision term in modulation/ demodulation indices.

Use of neural network to in situ conditioning of semiconductor plasma processing equipment

A strategy for in situ fault detection of plasma equipment is presented. This was accomplished by combining optical emission spectroscopy (OES), neural network. The OES was used to collect fault spectra, inducted by radio frequency source and bias powers. A fault detection model was constructed by training the backpropagation neural network (BPNN) on the whole OES spectrum representing a normal plasma operation. The trained BPNN model was tested on the test data generated at other powers. The test result indicates that the BPNN model was capable of detecting abnormal plasma caused by a small variation of 1% in the source power. Due to less impact on the plasma properties, the BPNN model reacted sensitively only to a relatively large variation in the bias power. The performance of the BPNN model-based monitoring scheme was further compared to that of identified radicals. Much improved sensitivity of the BPNN model over them was clearly demonstrated for the source power variation. On the other hand, certain radicals yielded much improved detection for the bias power variation. This was manifest as plasma was monitored by means of the CUSUM control chart. In consequence, monitoring BPNN model-based prediction and identified radicals simultaneously is expected to provide an improved detection of plasma processing equipment.

Electromagnetic surface modes in a magnetized quantum electron-hole plasma

The propagation of surface electromagnetic waves along a uniform magnetic field is studied in a quantum electron-hole semiconductor plasma. A forward propagating mode is found by including the effect of quantum tunneling. In the classical limit (ħ→0), one of the low-frequency modes found is similar to an experimentally observed one in n-type InSb at room temperature. The surface modes are shown to be significantly modified in the case of high-conductivity semiconductor plasmas where electrons and holes may be degenerate. The effects of the external magnetic field and the quantum tunneling on the surface wave modes are discussed.

Workshop on atomic and molecular collision data for plasma modelling: database needs for semiconductor plasma processing

The process time for semiconductor fabrication has a great influence on both the gas phase and the material surface. We have to consider two specific phenomena when we simulate, predict or design a plasma process for materials. One is the temporal change in the plasma structure and function through the change in feed gas molecules, and the other is the temporal change in surface morphology. On the other hand, the plasma surface process is a competition among etching, deposition and charging caused by active ions and neutral radicals incident on the surface. We show and discuss the present stage of the database in the gas phase and on the surface phase of plasma etching employed in semiconductor manufacturing.

Thermally tunable and omnidirectional terahertz photonic bandgap in the one-dimensional photonic crystals containing semiconductor InSb

Thermally tunable and omnidirectional terahertz (THz) photonic bandgaps in the one-dimensional photonic crystals composed of alternating layers of semiconductor material InSb and dielectric material SiO2 are studied theoretically. This photonic bandgap is strongly dependent on the lattice constants and the thickness ratio of the constituent InSb and SiO2 layers. It is found that the lower-order gap is invariant on the lattice constants, but the higher-order gaps are all sensitive to the lattice constants. Moreover, the band-edges of the higher-order gaps shift to lower frequency as the increasing thickness ratio. Additionally, the Gap II is also angle-independent, and the omnidirectional bandgap can occur in the terahertz range. Omnidirectional bandwidth for both polarizations is about 1.5 THz at 220 K. Most important of all, the omnidirectional bandgap can be tuned by controlling the external temperature, which results from the dependence of the semiconductor plasma frequency on the temperature. As the temperature increases, the upper and lower frequency limits of the Gap II shift to higher frequency and the bandwidth becomes narrow.

Photon creation in a resonant cavity with a nonstationary plasma mirror and its detection with Rydberg atoms

We investigate the dynamical Casimir effect and its detection with Rydberg atoms. The photons are created in a resonant cavity with a plasma mirror of a semiconductor slab which is irradiated by periodic laser pulses. The canonical Hamiltonian is derived for the creation and annihilation operators, showing the explicit time variation in the couplings, which originates from the external configuration such as a nonstationary plasma mirror. The number of created photons is evaluated as squeezing from the Heisenberg equations with the Hamiltonian. Then the detection of the photons as the atomic excitations is examined through the atom-field interaction. Some consideration is made for a feasible experimental realization with a semiconductor plasma mirror.

Effect of carrier heating on diffusion induced modulational instability in semiconductor plasmas

The purpose of the present paper is to report the study on modulational amplification in diffusive semiconductors including hot carrier effects. Considering that the origin of modulational interaction lies in the third-order optical susceptibility χ(3) arising from the nonlinear diffusion current density and using coupled mode theory, an analytical investigation of frequency modulational interaction between co-propagating laser beams and internally generated acoustic mode is presented. We have studied the steady state and transient amplification characteristics of modulated waves arising in diffusive semiconductor plasmas. The effect of carrier heating adds new dimensions to the present study. The heating effect reduces the required threshold amplitude of wave and enhances steady-state as well as transient gain of the generated acoustic mode.

Electron–Phonon Coupling Effects on the Karpman–Washimi Ponderomotive Magnetization in a Semiconductor Plasma

In recent years, there has been a considerable interest in the physical properties of semiconductor quantum plasmas since the ion implantation technique has been widely used as an effective nano-fabrication tool for manufacture of various semiconductor components. In quantum plasmas, the linear and nonlinear dispersion properties of plasma waves including the Bohm potential term due to the collective behavior have been considerably investigated by using the quantum hydrodynamic model. Very recently, the lattice electron– phonon effects are explored in a homogeneous piezoelectric semiconductor quantum plasma and is also found that the electron–phonon coupling generates the far-field dynamically oscillatory wake field. In various plasmas, the wave propagation and trapping have been extensively explored by the ponderomotive interactions between the electromagnetic field and plasma since the ponderomotive force provides the spectral characteristics of the plasma. It has been also shown that the ponderomotive interaction in plasmas would be obtained as the space–time derivatives of the stress tensor. However, the physical characteristics of the Karpman– Washimi ponderomotive magnetization caused by the timevariation of the intensity of the electromagnetic field in a homogeneous piezoelectric semiconductor quantum plasma including the influence of the electron–phonon interactions have not been investigated as yet. Hence, in this paper we have investigated the electron–phonon interaction effects on the non-stationary Karpman–Washimi ponderomotive magnetization in a semiconductor quantum plasma. Hence, the induced electron cyclotron motion due to the Karpman– Washimi ponderomotive force of the electromagnetic wave has been investigated as a function of the electron plasma frequency, quantum angular frequency, speed of the acoustic phonon, and electron–phonon coupling coefficient. From the Karpman–Washimi procedure, the total Karpman–Washimi ponderomotive force FKW of the electromagnetic field ~ Eðr; tÞ 1⁄21⁄4 ðEðr; tÞeiðk r !tÞ þ E ðr; tÞe iðk r !tÞÞ=2 in unmagnetized plasmas would be expressed as follows:

Coupling electron-hole and electron-ion plasmas: Realization of an npn plasma bipolar junction phototransistor

Coupling e−–h+ and gas phase plasmas with a strong electric field across a potential barrier yields a transistor providing photosensitivity and voltage gain but also a light-emitting collector whose radiative output can be switched and modulated. This optoelectronic device relies on the correspondence between the properties of a low temperature, nonequilibrium plasma and those for the e−–h+ plasma in an n-type semiconductor. Hysteresis observed in the collector current-base current characteristics is attributed primarily to charge stored in the base, and the photogeneration of e−–h+ pairs at the base-collector junction. Extinguishing the collector plasma requires an emitter-base junction reverse bias of <1 V.

반도체 플라즈마 식각 시스템의 균일도 향상을 위한 CCP와 ICP 결합 임피던스정합 장치

This paper proposes a DFPS (Dual Frequency Power Source) impedance matching device for uniformity improvement of a semiconductor plasma etching system. The DFPS consists of two parts for safe plasma processing on large-area substrates. The first part is an ICP (Inductively Coupled Plasma) for high integration by using ferrite core. The second part is a CCP (Capacitive Coupled Plasma) to control uniformity of whole cells. Proposed DFPS can achieve high productivity improvement required for semiconductor equipment industry. The proposed plasma system is analyzed, simulated and experimentally verified with a matching equipment at 27.12MHz and 400kHz.

Plasma Wave Electronics: A Revival Towards Solid-State Terahertz Electron Devices

Researches on the interactions between drifting carrier plasma waves and electromagnetic waves were intensively studied theoretically and experimentally in 1960s to 1990s but faded out with inconclusive results. This study presents a series of fundamental works carried out by our group in order to re-evaluate the possibility of realizing a solid-state amplifier operating in THz region based on the drifting plasma wave interactions. Firstly, we described a new method to analyze the properties of semiconductor drifting plasma in a semiconductor-insulator structure based on the Transverse Magnetic (TM) mode analysis. The components of waves, the electromagnetic fields and the ω- and k- dependent effective permittivity which are used to describe the dielectric response of the semiconductor plasma to the TM surface wave excitation are derived. Then, the properties of semiconductor drifting plasma in a two-dimensional electron gas (2DEG) structure using the developed TM mode analysis are presented. Here, the electromagnetic fields and the ω- and k- dependent effective permittivity of the 2DEG drifting plasma are also determined. The analyzed device structure and formulation procedures to explain the interactions between drifting plasma waves in semiconductor and electromagnetic waves propagating through the interdigital slow-wave structure is then presented. Next, some preliminary experimental studies of plasma wave interactions using interdigital-gated n-AlGaAs/GaAs high-electron-mobility-structure carried out are presented. Finally, we concluded the findings or contributions of our work and some remarks for future research.

Solid-state traveling-wave amplifiers and oscillators in the THz range: effect of electron collisions

Due to their high plasma frequencies, drifting semiconductor plasmas interacting with slow electromagnetic waves hold promise for terahertz amplifiers and oscillators. In these devices, the gain and the type of instabilities are influenced by electron collisions. To study the effect of collisions, we developed a two-wave model describing the interaction between drifting solid-state plasmas and electromagnetic waves. This paper analyzes the two-wave dispersion relation for representative examples. As the examples show, convective and absolute instabilities can occur at high and low collision frequencies depending on the relationship between the collision frequency and the coupling coefficient. Surprisingly, an absolute instability occurs when collision-dominated plasmas interact with backward waves. The model can be used to determine the potential of a particular configuration in a solid-state amplifier or oscillator.

Diffusion-induced modulational instability in magnetised semiconductor plasmas: effect of carrier heating

The present paper is aimed to the exploration of modulational amplification in transversely magnetised diffusive semiconductors. By considering that the origin of modulational interaction lies in the third-order optical susceptibility \(\chi^{(3)}\) arising from the nonlinear diffusion current density and using coupled mode theory, an analytical investigation of frequency modulational interaction between co-propagating laser beams and internally generated acoustic mode is presented. We have studied the steady state and transient amplification characteristics of modulated waves arising in the transversely magnetised semiconductor plasmas. The effect of carrier heating adds new dimensions to the present study. The heating effect reduces the required threshold amplitude of wave and enhances steady-state as well as transient gain of the generated acoustic mode.

Optically excited plasmaelastic waves in semiconductor plate-coupled plasma and elastic phenomena

A system of coupled plasma and elastic waves (the plasmaelastic waves) equations are analyzed. The treatment considers a semiconductor elastic plate with isotropic and homogeneous plasma and elastic properties. The solution of the coupled system of plasma and elastic equations are given for a typical photothermal configuration including the carrier surface and volume recombination processes. The analysis of the plasma density and elastic fields shows that the coupling plasmaelastic effects show the attenuation and disperse phenomena.