The transport properties of modulation, shifted modulation, and uniformly doped Al0.20Ga0.80N/GaN superlattices are presented. The modulation-doped sample is doped only in the AlGaN barriers. The shifted-modulation-doped sample has its dopants shifted by one-quarter period. Measurements reveal a strong improvement in mobility and resistivity for the modulation-doped and shifted-modulation-doped structures versus the uniformly doped structure. The modulation-doped sample has a mobility of 9.2 and 36 cm2/V s at 300 and 90 K respectively and a very low resistivity of 0.20 and 0.068 Ω cm at 300 and 90 K, respectively. Capacitance–voltage profiling shows multiple two-dimensional hole gases. The results are consistent with a reduction of neutral impurity scattering for modulation-doped structures as compared to uniformly doped structures.

Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices J. Appl. Phys. 112, 063714 (2012) Polarization Coulomb field scattering in In0.18Al0.82N/AlN/GaN heterostructure field-effect transistors J. Appl. Phys. 112, 054513 (2012) Modulation doping to control the high-density electron gas at a polar/non-polar oxide interface Appl. Phys. Lett. 101, 111604 (2012) Ultra low-resistance palladium silicide Ohmic contacts to lightly doped n-InGaAs

An electrically conductive omnidirectional reflector (ODR) is demonstrated in an AlGaInP light-emitting diode (LED). The ODR serves as p-type contact and comprises the semiconductor, a metal layer and an intermediate low-refractive index dielectric layer. The dielectric layer is perforated by an array of AuZn microcontacts thus enabling electrical conductivity. It is shown that the ODR significantly increases light extraction from an AlGaInP LED as compared to a reference LED employing a distributed Bragg reflector (DBR). External quantum efficiencies of 18% and 11% are obtained for the ODR-and the DBR-LED, respectively.

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Perpendicular transport characteristics of n-type AlxGa1−xN/GaN superlattices are presented. Planar and mesa-etched superlattice structures are employed to identify the perpendicular resistance. Perpendicular transport measurements in Al0.22Ga0.78N/GaN superlattices display linear current–voltage characteristics with a resistivity that is a factor of 6.6 higher than for bulk material. A theoretical model is developed for perpendicular transport in AlxGa1−xN/GaN superlattices based on sequential tunneling. The model shows that short superlattice periods are required to minimize the perpendicular resistivity.