Analytic theory for current-voltage characteristic of a nanowire radial p-i-n diode

In this article, process of current flow in a nanowire radial p-i-n diode has been considered in detail. It has been shown that cylindrical geometry of the structure gives rise to specific asymmetry of the concentration distribution for current carriers injected to the i-layer, which is opposite to asymmetry that is due to inequality of carriers’ mobilities. This specific asymmetry rises with bringing the i-layer nearer to the nanowire center. Together with that, decrease of the current density in a “long” p-i-n diode and its increase in a “short” p-i-n diode take place (at given forward voltage). And variation of radial thickness of the i-layer demonstrates maximums in the current density at the thickness close to the bipolar diffusion length.

The Influence of Design on Electrical Performance of AlGaN/GaN Lateral Schottky Barrier Diodes for Energy-Efficient Power Applications

In this paper, lateral AlGaN/GaN Schottky barrier diodes are investigated in terms of anode construction and diode structure. An original GaN Schottky diode manufacturing-process flow was developed. A set of experiments was carried out to verify dependences between electrical parameters of the diode, such as reverse and forward currents, ON-state voltage, forward voltage and capacitance, anode-to-cathode distance, length of field plate, anode length, Schottky contact material, subanode recess depth, and epitaxial structure type. It was found that diodes of SiN/Al0.23Ga0.77N/GaN epi structure with Ni-based anodes demonstrated two orders of magnitude lower reverse currents than diodes with GaN/Al0.25Ga0.75N/GaN epitaxial structure. Diodes with Ni-based anodes demonstrated lower VON and higher IF compared with diodes with Pt-based anodes. As a result of these investigations, an optimal set of parameters was selected, providing the following electrical characteristics: VON = 0.6 (at IF = 1 mA/mm), forward voltage of the diode VF = 1.6 V (at IF = 100 mA/mm), maximum reverse voltage VR = 300 V, reverse leakage current IR = 0.04 μA/mm (at VR = −200 V), and total capacitance C = 3.6 pF/mm (at f = 1 MHz and 0 V DC bias). Obtained electrical characteristics of the lateral Schottky barrier diode demonstrate great potential for use in energy-efficient power applications, such as 5G multiband and multistandard wireless base stations.

Improving Emission Uniformity of InGaN/GaN-Based Vertical LEDs by Using Reflective ITO/Ag n-Contact

We investigated the effect of Ti/Al and ITO/Ag n-type contacts on the emission uniformity and light output of different chip-size vertical-geometry light-emitting diodes (VLEDs) for vehicle headlamp application. The forward voltage of the Ti/Al-based reference VLEDs decreased from 3.38 to 3.20 V at 1500 mA with increasing chip size from (1280 × 1000 µm2) to (1700 × 1700 µm2), whereas that of the ITO/Ag-based samples changed from 3.37 to 3.15 V. Regardless of chip size, the ITO/Ag-based samples revealed higher light output power than the reference samples. For example, the ITO/Ag-based samples (chip size of 1700 × 1700 µm2) exhibited 3.4% higher light output power at 1500 mA than the reference samples. The ITO/Ag samples underwent less degradation in the Wall-plug efficiency (WPE) than the reference sample. For instance, the ITO/Ag-based samples (1700 × 1700 µm2) gave 4.8% higher WPE at 1500 mA than the reference samples. The ITO/Ag-based samples illustrated more uniform emission than the Ti/Al-based sample. Both the reference and ITO/Ag-based samples underwent no degradation when operated at 1500 mA for 1000 h.

Design and Simulation of an Electrically Pumped SPASER

In this investigation, a novel SPASER is designed and simulated which uses a forward biased pn junction to induce population inversion condition. Simulations are performed by means of SILVACO software. In the proposed structure, the active region is considered as a direct bandgap material (InGaAs) and a larger bandgap material (InP) is used for p and n regions to form heterojunctions. This pn junction is in contact with gold and surface plasmons propagate along their interface. Free space wavelength of the oscillations of surface plasmons is 1550nm that is used in photonic devices, frequently. To form the resonance cavity of the SPASER, two high reflective mirrors are placed at the ends of the plasmonic waveguide. Applied forward voltage and absorption coefficient of the SPASER are 1.2V and − 0.33cm− 1, respectively. Thus, the optical gain for a 50 microns cavity length is 1cm− 1. Moreover, the power consumption of the proposed device at these conditions is 1.2mW. The output plasmonic power is 0.6mW which yields 50% power efficiency.