• Journal of the Microelectronics and Packaging Society
• /
• v.28 no.4
• /
• pp.85-89
• /
• 2021

AlGaN-based UV-C light-emitting diodes (LEDs) were applied for p-type activation by electrochemical potentiostatic activation (EPA). The p-type activation efficiency was increased by removing hydrogen atoms through EPA treatment using a neutral Mg-H complex that causes high resistance and low conductivity. A neutral Mg-H complex is decomposed into Mg^- and H⁺ depending on the key parameters of solution, voltage, and time. The improved hole carrier concentration was confirmed by secondary ion mass spectroscopy (SIMS) analysis. This mechanism eventually improved the internal quantum efficiency (IQE), the light extraction efficiency, the leakage current value in the reverse current region, and junction temperature, resulting in better UV-C LED lifetime. For systematic analysis, SIMS, Etamax IQE system, integrating sphere, and current-voltage measurement system were used, and the results were compared with the existing N₂-annealing method.

• Journal of the Korean Vacuum Society
• /
• v.19 no.1
• /
• pp.10-13
• /
• 2010

We studied the effect of $O_2$ plasma treatments on the electrical property of Ti / Al ohmic contacts to N-face n-type GaN. The surface of N-face, n-type GaN has been treated with $O_2$ plasma for 120 s before the deposition of bilayered electrodes, Ti (50 nm) / Al (35 nm), and its contact resistance was compared with that of the reference sample without $O_2$ plasma. As a result, we found that the ohmic contact was reduced from $4.3\;{\times}\;10^{-1}\;{\Omega}cm^2$ to $1.25\;{\times}\;10^{-3}\;{\Omega}cm^2$ by applying $O_2$ plasma on the surface of n-type GaN, which was attributed to the reduction in the Schottky barrier height (SBH), caused by nitrogen vacancies formed during the $O_2$ plasma process.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.25 no.11
• /
• pp.1373-1379
• /
• 1988

This paper describes a two-dimensional analysis of the potential distribution and electron concentration of the MODFET at channel using FDM. More exact analysis can be obtained by two-dimensional analysis which considers parasitic effects ignored in one-dimensional analysis. Using Poisson and Shrodinger equations, the potential distribution and the wave function are calculated within a constant error bound. As a result, the relations between the thickness of spacer, doping concentration of (n) AlGaAs layer, and the sheet density of the 2DEG (2 Dimensional Electron Gas) of MODFET at channel are suggested quantitively. The sheet density of the 2DEG is increased as the thickness of the spacer is decreased of the doping concentration of the (n)AlGaAs layer is lowered.

• Journal of the Korean Vacuum Society
• /
• v.12 no.4
• /
• pp.218-227
• /
• 2003

Pd/Si/Ti/Pt and Pd/Si/Pd/Ti/Au ohmic contacts to n-type InCaAs were investigated for applications to AlGaAs/GaAs HBT emitter ohmic contacts. In the Pd/Si/Ti/Pt ohmic contact, as-deposited contact showed non-ohmic behavior, and high specific contact resistivity of $5\times10^{-3}\Omega\textrm{cm}^2$ was achieved by rapid thermal annealing at $375^{\circ}C$/10 sec. However, the specific contact resistivity decreased remarkably to $2\times10^{-6}\Omega\textrm{cm}^2$ by annealing at $425^{\circ}C$/10sec. In the Pd/Si/Pd/Ti/Au ohmic contact, minimum specific contact resistivity of $3.9\times10^{-7}\Omega\textrm{cm}^2$ was achieved by annealing at $400^{\circ}C$/20sec. In both ohmic contacts, low contact resistivity and non-spiking planar interface between ohmic materials and InGaAs were maintained. Therefore, these thermally stable ohmic contact systems are promising candidates for compound semiconductor devices. RF performance of the AlGaAs/GaAs HBT was also examined by employing the Pd/Si/Ti/Pt and Pd/Si/Pd/Ti/Au systems as emitter ohmic contacts. Cutoff frequencies were 63.9 ㎓ and 74.4 ㎓, respectively, and maximum oscillation frequencies were 50.1 ㎓ and 52.5 ㎓, respectively. It shows very successful high frequency operations.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.3C no.2
• /
• pp.66-69
• /
• 2003

Various semiconductor nanowires such as GaN, GaP, InP, Si$_3$N$_4$, SiO$_2$/Si, and SiC were coated conformally with aluminum oxide (Al$_2$O$_3$) layers by atomic layer deposition (ALD) using trimethylaluminum (TMA) and distilled water ($H_2O$) at a temperature of 20$0^{\circ}C$. Transmission electron microscopy (TEM) revealed that A1203 cylindrical shells conformally coat the semiconductor nanowires. This study suggests that the ALD of $Al_2$O$_3$ on nanowires is a promising method for preparing cylindrical dielectric shells for coaxially gated nanowire field-effect transistors.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.5
• /
• pp.490-496
• /
• 2015

We have grown AlN/GaN heterostructure which is a promising candidate for mm-wave applications. For the growth of the high quality very thin AlN barrier, indium was introduced as a surfactant at the growth temperature varied from 750 to $1070^{\circ}C$, which results in improving electrical properties of two-dimensional electron gas (2DEG). The heterostructure with barrier thickness of 7 nm grown at of $800^{\circ}C$ exhibited best Hall measurement results; such as sheet resistance of $215{\Omega}/{\Box}$electron mobility of $1430cm^2/V{\cdot}s$, and two-dimensional electron gas (2DEG) density of $2.04{\times}10^{13}/cm^2$. The high electron mobility transistor (HEMT) was fabricated on the grown heterostructure. The device with gate length of $0.2{\mu}m$ exhibited excellent DC and RF performances; such as maximum drain current of 937 mA/mm, maximum transconductance of 269 mS/mm, current gain cut-off frequency of 40 GHz, and maximum oscillation frequency of 80 GHz.

• Korean Journal of Materials Research
• /
• v.13 no.7
• /
• pp.465-472
• /
• 2003

Pd/Ge/Ti/Pt and Pd/Ge/Pd/Ti/Au ohmic contacts to n-type InGaAs were investigated for applications to AlGaAs/GaAs HBT emitter ohmic contacts. In the Pd/Ge/Ti/Pt ohmic contact minimum specific contact resistivity of $3.7${\times}$10^{-6}$ $\Omega$$\textrm{cm}^2$ was achieved by rapid thermal annealing at $^400{\circ}C$/10 sec. In the Pd/Ge/Ti/Au ohmic contact, minimum specific contact resistivity of $1.1${\times}$10^{-6}$ $\Omega$$\textrm{cm}^2$ was achieved by annealing at 40$0^{\circ}C$/10 sec but the ohmic performance was degraded with increasing annealing temperature due to the reaction between the ohmic contact materials and the InGaAs substrate. However, non-spiking planar interface and relatively good ohmic contact (high-$10^{-6}$ /$\Omega$$\textrm{cm}^2$) were maintained after annealing at $450^{\circ}C$/10 sec. Therefore, these thermally stable ohmic contact systems are promising candidates for compound semiconductor devices. RF performance of the AlGaAs/GaAs HBT was also examined by employing the Pd/Ge/Ti/Pt and Pd/Ge/Pd/Ti/Au systems as emitter ohmic contacts. Cutoff frequencies were 63.5 ㎓ and 65.0 ㎓, respectively, and maximum oscillation frequencies were 50.5 ㎓ and 51.3 ㎓, respectively, indicating very successful high frequency operations.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.4 no.3
• /
• pp.217-221
• /
• 2004

[ $CO_2$ ]laser ablation rates for bulk 4H-SiC substrates and GaN/AIN/SiC templates in the range 229-870 ${\mu}m.min^{-1}$ were obtained for pulse energies of 7.5-30 mJ over diameters of 50·500 ${\mu}m$ with a Q-switched pulse width of ${\sim}30$ nsec and a pulse frequency of 8 Hz. The laser drilling produces much higher etch rates than conventional dry plasma etching (0.2 - 1.3 ${\mu}m/min$) making this an attractive maskless option for creating through-wafer via holes in SiC or GaN/AlN/SiC templates for power metal-semiconductor field effect transistor applications. The via entry can be tapered to facilitate subsequent metallization by control of the laser power and the total residual surface contamination can be minimized in a similar fashion and with a high gas throughput to avoid redeposition. The sidewall roughness is also comparable or better than conventional via holes created by plasma etching.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.955-959
• /
• 2004

The effects of conduction band offset on 2 dimensional electron gas (2DEG) in N-InAlAs(AlAsSb)/InGaAs/InAlAs (AlAsSb) metamorphic heterostructures (MMHS) are studied. A combination of the Shubnikov-deHaas oscillations and the Hall measurements is used to investigate the electron transport properties of these structures. The mobility in the second subband is higher than that in the first subband in all heterostructures. This is attributed to the fact that electrons in the first subband we, on average, closer to the interface and are therefore scattered more strongly by ionized impurities. The results suggest that intersubband scattering rate is more dominant in structures with higher conduction band offset whereas alloy scattering is found to be more dominant in the higher band offset system.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.637-640
• /
• 1998

A 35 ㎓ GaAs MMIC power amplifier was designed using a monolithic technology with AlGaAs/InGaAs/GaAs power PM-HEMTs, rectangualr spiral inductors and Si3N4 MIM capacitors. The GaAs power MESFETs in the input and output stages have total gate widths of 120 um and 320 um, respectively. Total S21 gain of 10.82dB and S11 of -16.26 dB were obtained from the designed MMIC power amplifier at 35 ㎓. And the chip size of the MMIC amplifier was 1.4$\times$0.8 $\textrm{mm}^2$