Asymmetric Multiple Quantum Well Research Articles

Nonuniform carrier distribution in asymmetric multiple-quantum-well InGaAsP laser structures with different numbers of quantum wells

A method for quantifying the degree to which the uneven carrier distribution affects the operation of multiple quantum well (MQW) lasers is developed by comparing the net gains of wells in mirror image asymmetric MQW structures. The uneven carrier distribution is found to affect the performance of devices with as few as two quantum wells and decreases the net gain for wells on the n side of a ten quantum well structure by more than a factor of two.

Effect of barrier height on the uneven carrier distribution in asymmetric multiple-quantum-well InGaAsP lasers

Four asymmetric multiple-quantum-well (AMQW) laser structures have been grown and tested. The structures demonstrate that carriers are not evenly distributed across the active region of a MQW laser. Wells at the p-side of the active region are preferentially pumped indicating there are more carriers at the p-side of the active region than at the n-side. The structures also demonstrate that decreasing the height of the barriers reduces this effect and results in a more even carrier distribution. Thus, well position and barrier height are shown to be important design parameters for AMQW and conventional MQW lasers.

K-band operation of asymmetric Fabry-Perot modulators

The authors report preliminary high-frequency, small-signal optical measurements of asymmetric multiple-quantum well (MQW) Fabry-Perot electrooptic modulators which indicate that the electrical bandwidth for these devices is about 15 GHz at the onset of saturation, and as high as 21 GHz at low optical intensity-higher than any other measurements published to date. The modulators, 30 mu m*30 mu m in size, are integrated with on-chip microwave probe pads. The authors detail the fabrication process developed to achieve these high operating frequencies and predict from device models the maximum RC-limited operating frequencies for these devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Vertical transport, transmission coefficients, and dwell time in asymmetric quantum well structures

The transport of hot electrons in the Al xGa 1−xAs barriers above the wells in a multiple quantum well (MQW) structure is investigated. The structures that are studied are asymmetric quantum well infrared detectors. The transport of the hot electrons normal to the layers is strongly dependent on both voltage and well shape. It is suggested that the key parameter which affects the transport properties is the dwell time of the electrons in the continuum, above the well region. This is most readily seen in asymmetric MQW structures, in which the dwell time under an applied bias depends very strongly on bias polarity. Calculations of electron transmission coefficient and dwell time show that the electron mean free path in asymmetric wells is much larger in positive bias than in a negative one. Employing this model, we achieve a very good fit to experimental data.