Hsin-Chuan Wang

InGaN/GaN Light Emitting Diodes with a Lateral Current Blocking Structure

The light output of InGaN/GaN light-emitting diodes (LEDs) was improved by introducing a current blocking hole between the n-type and p-type bonding pads. The injected current was forced to spread out instead of directly passing along the nearest path between the p-type and n-type bonding pads. The light output of the LED with a current blocking hole at 20 mA was 7.2% higher than that of the conventional LED. The forward voltage of the LED with the blocking hole was 3.29 V at 20 mA, which is slightly higher than that of the conventional LED (3.26 V). LEDs with different current blocking hole sizes were also studied.

AlGaInP Light Emitting Diode with a Modulation-Doped Superlattice

AlGaInP light-emitting diode (LED) with a GaP/In0.5Ga0.5P modulation-doped superlattice was grown by metal organic chemical vapor deposition (MOCVD). The luminous intensity was increased by a factor of 1.16 at 20 mA and of 1.5 at 100 mA with the benefit of the modulation-doped superlattice. The enhanced current-spreading ability offered by the modulation-doped superlattice was demonstrated by the analysis of dynamic resistance under different operation voltage. In addition, the superior current spreading also brought about less generation of heat, which can be manifested by the electroluminescence (EL) spectrum with increase of the injection current.

Improvement of AlGaInP light emitting diode by sulfide passivation

The brightness of AlGaInP light emitting diodes (LEDs) has been raised by a factor of 1.12 at 20 mA by sulfide passivation. Meanwhile, the sulfide also can decrease leakage current of AlGaInP LEDs at -2 V to nearly one thousandth of that in the as-fabricated device. The possible causes for the brightness increase of AlGaInP LEDs after sulfide treatment including surface roughness, reduction of Fresnel loss, and effective injection of carriers were demonstrated.

Well width dependence for novel AlInAsSb/InGaAs double-barrier resonant tunneling diode

Abstract The novel Al 0.66 In 0.34 As 0.85 Sb 0.15 /In 0.53 Ga 0.47 As heterostructure has a large conduction band offset (about 1 eV). Taking the advantage of high conduction-band offset, it has been demonstrated to be a potential candidate for double-barrier resonant tunneling diodes (DBRTDs). Well width is an important parameter for the performance of a DBRTD. We fixed the barrier width and discussed the well width dependence for Al 0.66 In 0.34 As 0.85 Sb 0.15 /In 0.53 Ga 0.47 As DBRTD. Peak current densities exhibit a maximum at the 4 nm well width. A peak-to-valley current ratio of 46 with a peak current density of 22 kA/cm 2 at room temperature was demonstrated for the 4 nm-InGaAs-well.

Improvement of AlGaInP Multiple-Quantum-Well Light-Emitting Diodes by Modification of Ohmic Contact Layer

A meshed contact layer was proposed to enhance the current-spreading ability of AlInGaP light-emitting diodes (LEDs). Via the modification of the contact layer, the luminous intensity was increased by a factor of 1.16 compared with that of the conventional LEDs at a wavelength of 570 nm. Moreover, the brightness reliability of such a new structure was found to be superior to that of conventional structures.

Fabrication of Oxide-Confined Collector-Up Heterojunction Bipolar Transistors.

The first fabrication and current-voltage characteristics of oxide-confined collector-up heterojunction bipolar transistors (HBTs) were reported. A partially oxidized Al0.98Ga0.02As layer was introduced between the base layer and the emitter layer to reduce the base leakage current. The current gain and the turn-on voltage of the fabricated HBT were 16 and 1.07 V, respectively.

Improved 634 nm MQW AlGaInP LEDs performance with novel tensile strain barrier reducing layer

Light-emitting diodes (LEDs) under long-term or high-current operating undergo significant performance change and degradation with time. Thus a novel Ga/sub x/In/sub 1-x/ P tensile strain barrier reducing (TSBR) structure is grown between window and cladding layers of multi-quantum-well-AlGaInP LEDs. The TSBR (/spl sim/ 150 AGa/sub x/In/sub 1-x/P) film is of lattice size and valence band energy intermediate between those of window and cladding layers, thus reducing band offset. Experimental characterization shows significant decrease in device forward bias, dynamic resistance and junction heating, with strong improvement in power output degradation for the high current region. Various compositions of Ga/sub x/In/sub 1-x/P TSBR are fabricated, aged at dc 50 mA, and tested at nonradiative and radiative current levels. Optimal Ga/sub x/In/sub 1-x/P composition is determined. Two separate power output degradation mechanisms are noted and discussed. In sum, the TSBR layer appears a highly successful design for improved power efficiency, reliability and global lifetime behavior of an LED-type device.

Improvement of AlInP-AlGaInP MQW light-emitting diode by meshed contact layer

The optical output power of the AlInP-AlGaInP light-emitting diodes was pronouncedly enhanced 1.45 times at 20 mA without degrading the electrical characteristics by introducing the meshed GaAs contact layer. Both theoretical simulation and experimental analysis were used to demonstrate the feasibility of the proposed structure.

Characteristics and improvement in hot-carrier reliability of sub-micrometer high-voltage double diffused drain metal-oxide-semiconductor field-effect transistors

The hot-carrier reliability of 12 V high-voltage n-channel double diffused drain metal–oxide–semiconductor (DDDMOS) field-effect transistors with various n-type double diffusion (NDD) implant dosages is investigated. A high NDD implant dosage results in a high substrate current; however, on-resistance (Ron) degradation is low. The damage location shifting toward the channel is responsible for this unexpected low Ron degradation. Technology computer-aided design (TCAD) simulation and charge pumping measurements are carried out to identify the damage location. Our analysis results reveal that an increase in NDD dosage is effective for improving the reliability of the DDDMOS field-effect transistors.

Elimination of burn-in effect in carbon-doped InGaP/GaAs HBTs by hydrogen lateral diffusion

Abstract Hydrogen lateral diffusion by annealing at low temperature was proposed to eliminate the burn-in effect in carbon-doped InGaP/GaAs heterojunction bipolar transistors (HBTs). After a thermal annealing at 480 °C for 30 min, the current gain variations caused by the electrical stress decreased from 42.7% to 2.6% as the emitter width was reduced from 100 to 5 μm. After the annealing process, the sheet resistance was decreased from 194.4 to 162.7 ohm/sq. as the van der Pauw line widths was reduced from 65 to 5 μm. Effective doping concentration in base layer was increased by removal of incorporated hydrogen atoms. Degradation of device characteristics was not obvious after annealing by comparing the ratio difference of current gain to base sheet resistance.