Multiple Quantum Barrier Research Articles

Novel GaAs Metal–Semiconductor Field-Effect Transistors with InGaP/GaAs Multiple Quantum Barrier Capping and Buffer Layers

We present a novel GaAs metal–semiconductor field-effect transistor (MESFET) with InGaP/GaAs multiple quantum barrier (MQB) capping and buffer layers. The MQB structure with (29; 6, 5, 7; 8, 8, 1; 6, 5, 7; 29) periodic stacks was designed to increase effective-potential-barrier height. We demonstrate that, by using the InGaP/GaAs MQB capping layer, the gate Schottky barrier performance and gate leakage current are improved.

An atomic force microscope-based investigation of vertical transport through GaAs/GaAlAs/InAlAs/GaAs step-barrier heterostructures

Study of vertical transport through heterostructures consisting of single, double, or multiple quantum barriers is of both fundamental and technological interest. While extensive data regarding electron transport is available for single- and double-barrier structures, relatively less information is available for transport through step-barrier structures. In this paper, we present results from a study of room temperature vertical transport through a GaAs/GaAlAs/InAlAs/GaAs multistep-barrier heterostructure. A typical atomic force microscope has been adapted to perform transport measurements, thus allowing precise control of the physical location of the region of measurement. I– V measurements reveal negative differential resistance (NDR) peaks, thus confirming the formation of resonant states in a triangular well created when a voltage bias is applied across the step barrier. I– V curves have also been calculated by numerically solving the Schrödinger wave equation for this step-barrier structure. Comparison between the measured and calculated I– V curves shows reasonable agreement in the number of NDR peaks. However, discrepancies exist between the measured and calculated values for the voltages at which these NDR peaks occur. Some possible reasons for these discrepancies are discussed in this work.

GaAs metal-semiconductor field effect transistor with InGaP/GaAs multiquantum barrier buffer layer

A novel metal-semiconductor field effect transistor (MESFET) with InGaP/GaAs multiple quantum barrier (MQB) buffer layer was studied. Since the effective potential barrier height is enhanced using the InGaP/GaAs MQB structure, good performances of electronic and optical isolations are achieved. A configuration with the MESFET and sidegate electrode was fabricated to demonstrate the function of the InGaP/GaAs MQB structure.

Predicting nonlinear electrical performance in single and multiple quantum-barrier varactors (QBV's) by the Monte Carlo technique

In this paper, nonlinear characterization and simulation of single and multiple quantum barrier varactors (QBV's) are obtained by using a multiparticle Monte Carlo simulator. The I-V relation is deduced directly from the equivalent charge variation and the bias voltage. The C-V characteristics are simply calculated from the width of the depletion region in a similar manner as for a parallel plate capacitor. The RF behavior is also simulated by modulating the voltage at 50 GHz and by performing an FFT of the current to study higher harmonic content of the QBV's. It is observed that only odd harmonics are generated and the current level of the third harmonic is about 10% of the injected signal current level. It is also shown that the use of multistack barriers can reduce the current density and the capacitance in accordance with the number of barriers in addition to increasing the breakdown voltage.

A new quantum structure ‘multiple quantum barrier and multiple quantum well in active region’ design for laser diode applications

A new quantum structure of AlGaAs laser for high temperature operation has been demonstrated. The new laser has a multiple-quantum barrier (MQB) structure located in the middle of the active region. This location of the MQB improves the efficiency of the hole injection into the active region compared to conventional MQB structure. It also maintains the suppressible effect of the electron overflow from the active region to the cladding layer. Moreover, multiple-quantum wells (MQWs) are integrated at each side of MQB to minimize the possible overflow of electrons by improving the recombination efficiency. The continuous-wave laser threshold current ( I th) and the differential quantum efficiency ( η d) have been improved about 50% by integration of MQW to the MQB in active laser. The I th as low as 31.1 mA ( η d: 0.44 mW/mA) was obtained on a ridge waveguide MQB + MQW in active laser of 4 μm wide and 300 μm long having as-cleaved uncoated facets.

A quantum structure for high-temperature operation of AlGaAs lasers: Multiple-quantum barrier and multiple-quantum well in active region

We propose a quantum structure of AlGaAs lasers designed for high-temperature operation. In this design, the superlattice structure multiple-quantum barrier (MQB) is located in the middle of active region which improves the injection efficiency of holes from the cladding into the active region, compared to MQB in cladding structure. Simulation results showed that low energy electrons can tunnel through the MQB barriers, while high energy electrons were reflected back by effective potential barrier to suppress the electron overflow from active to the cladding region. Multiple-quantum wells (MQWs) are integrated at each side of MQB to minimize the overflow of tunneled electrons. A differential quantum efficiency change as small as 5% was achieved in the temperature range of 20–100 °C from MQB+MQW in active lasers.

Carrier confinement by multiple quantum barriers in 1.55 μm strained GaInAs/AlGaInAs quantum well lasers

Carrier confinement performance by multiple quantum barriers (MQB) is demonstrated in 1.55 μm strained GaInAs/AlGaInAs multiple quantum well (MQW) lasers grown by molecular beam epitaxy. The strained MQW lasers with MQB at p-side optical confinement layer show larger characteristic temperature and slope efficiency at high temperature than those without MQB. It is also shown that the MQW lasers with MQB have less spontaneous emission from the optical confinement layer than the lasers without MQB. As another important result, it is demonstrated for the first time that the MQW lasers with MQB have less dependency of the K factor on the temperature than the lasers without MQB. These results further verify the effective carrier confinement performance of GaInAs/AlInAs MQB structure.

Theoretical Design of 460 nm ZnCdSSe Laser Diodes

Theoretical design of ZnSSe/ZnCdSSe laser diodes emitting 460 nm at room temperature (RT) was studied by means of threshold current analysis. The threshold current density calculation was based on the laser theory established for the III-V laser diode (LD) system. The result of the threshold current density calculation indicated that the reduction of carrier overflow is an essential issue in realizing the device with a reasonable threshold current level at RT. Another indication is that 30% S content in the ZnSSe cladding layer would be a suitable target value for a practical 460 nm LD at RT, along with a multiple quantum barrier structure. The predicted threshold current density of such a LD could be as low as 450 A/cm2 at RT.

A New Structure Design “Multiple-Quantum Barrier in Active Region” for High Temperature Operation of AlGaAs Superluminescent Diode

AbstractA multiple-quantum barrier (MQB) structure has been applied to AlGaAs superluminescent diode (SLD) to suppress the electron overflow from active to cladding region at elevated temperatures. It was found that the presence of MQB in the p-cladding region leads to stagnant hole transport to the active region. To improve the hole transportation, we propose a new quantum structure for active region. In this design, the superlattice structure MQB is located in the middle of active region which allows smooth hole injection to the active from the cladding region. Carriers can reach both side of the MQB structure in the active region by tunneling phenomenon which critically depends on the barrier thickness. Simulation results show that low energy electrons can tunnel through the MQB barriers, while high energy electrons are reflected back by effective barrier. Finally, multiple-quantum well (MQW) structure is integrated at each side of MQB to minimize the possible over-flow of tunneled electrons and to improve the radiative efficiency of the SLD device. Experimental data support the visibility of the proposed ‘MQB+MQW in Active’ structure at elevated temperatures.

Measurement of the barrier height of a multiple quantum barrier (MQB)

A method of using a light-emitting diode structure with two active regions to measure the excess barrier height induced by the inclusion of a multiple quantum barrier structure is outlined. For a multiple quantum barrier structure previously used in a visible laser device, the resultant increase in barrier height was found to be 26 meV. The effect of the first barrier thickness on the produced barrier height is also investigated. It was found that by optimizing this parameter, the induced barrier height could be increased to 55 meV. These results are compared with those predicted by theory, and certain discrepancies between them are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

AlGaInP strained multiple-quantum-well visible laser diodes ( lambda /sub L/&amp;gt;or=630 nm band) with a multiquantum barrier grown on misoriented substrates

Optimization of the misorientation angle of GaAs substrates to prepare multiple quantum wells (MQWS) and multiple quantum barriers (MQBs) with abrupt barrier-well interfaces is reported. The characteristics of AlGaInP strained MQW laser diodes incorporating an MQB grown on misoriented substrates are also investigated, with the aim of developing high-performance 630-nm laser diodes. MQW and MQB with homogeneous periodicity and abrupt barrier-well interfaces were obtained using

150 mW fundamental-transverse-mode operation of 670 nm window laser diode

Fundamental-transverse-mode high-power CW operation over 150 mW has been realized in AlGaInP/GaInP 670-nm window laser diodes. A window structure of Zn-induced-disordered GaInP has been fabricated by solid phase diffusion using ZnO film. A compressively strained double-quantum-well active layer and a multiple quantum barrier (MQB) also have been employed for reduction of threshold current. Stable CW operation beyond 1500 h has been observed under 50 mW at 50 degrees C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High temperature (74 degrees C) CW operation of 634 nm InGaAlP laser diodes utilizing a multiple quantum barrier

A modified multiple-quantum-barrier structure has been applied to a 630-nm-band laser diode. The result is a laser exhibiting a maximum operating temperature of 74 degrees C and a threshold current of 49 mA. These characteristics correspond to a 22 degrees C increase in the operating temperature and over a 50% decrease in the threshold current, in comparison to an identical laser without a multiple quantum barrier. This is the first time, to the authors' knowledge, that a significant decrease in the threshold current of a laser has been directly attributed to the influence of a multiple quantum barrier. >

Multiple quantum barrier structures and their application to high power visible laser diodes with strained InGaP active layers grown by MOCVD

We introduced a multiple quantum barrier (MQB) which was grown by MOCVD between the active layer and p-cladding layer to enhance potential barrier height. The MOCVD system was improved to realize the growth of MQB structures for the first time. We compared threshold current densities ( J th) of various barrier/well thickness combinations in order to optimize the MQB structure. We found that the thickness of barriers and wells should be 1.7 and 1.15 nm, respectively, to minimize J th. The optimized MQB significantly reduced the J th of visible laser diodes. Strained active layers with compressive stress were employed as another approach for the improvement of the threshold current. We found that the strained active layer is as effective as the MQB in reducing J th. The lowest J th has been achieved by the combination of MQBs and strained active layers. We realized an output power of 40 mW, at 90°C, at a lasing wavelength of 675 nm. to our knowledge, these are the best data.