Jong-Han Yang

Nanoscale dry etching of germanium by using inductively coupled CF4 plasma

The nanoscale dry etching of germanium was investigated by using inductively coupled CF4 plasma and electron-beam lithography. The optimal dose of PMMA as E-beam lithography resist was ∼200 mC/cm2. When ICP Power was 200W, CF4 gas flow rate was 40 sccm, and process pressure was 20 mTorr, it had a smooth surface and good etch rate. The etching selectivity of Ge wafer to PMMA resist was as low as ∼1.5. Various sub-100 nm dry-etching patterns have been obtained. SEM pictures showed good profile qualities with a smooth etching sidewall and ultrasmall etching features.

Robust ESD protection for high brightness GaN LEDs using new TVS Zener diodes

The electrostatic discharge (ESD) stability of GaN-based LEDs, which are assembled with new transient voltage suppression (TVS) Zener diodes, has been characterized in experiments on reverse leakage current and functionality. Advantageous features of TVS Zener diodes with extremely low differential resistance and low leakage current have enhanced their ESD protection capability, especially at high temperature. The TVS Zener presented an excellent performance in protecting GaN-based LEDs from ESD stress exceeding the human body model ±8 kV at 110 °C. The ESD robustness of the high-temperature stability is analyzed in order to provide proper reliability under hostile environment of massive heat and light delivered from LEDs.

Growth and characterization of Si1−xGetx QDs on Si/Si0.8Ge0.2 layer

Si1−xGetx QDs structures were grown onto Si/Si0.8Ge0.2 layer using RPCVD system. Ge composition in Si1−xGetx QDs was determined as about 30% and 40%. Three peaks are observed in Raman spectrum, which are located at about 520, 410, and 295 cm−1, corresponding to the vibration of Si-Si, Si-Ge, and Ge-Ge phonons, respectively, and the Si1−xGetx QDs related peak was located at 490 cm−1. The PL spectrum that originates from the radiative recombinations came from the Si substrate, the Si0.8Ge0.2 layer and Si1−xGetx QDs. For Si1−xGetx QDs, the transition peaks related to the QDs region observed in the photocurrent spectrum were preliminarily assigned to electron-heavy hole (e-hh) and electron-light hole (e-lh) fundamental excitonic transitions.

Selective Chemical Wet Etching of Si 0.8 Ge 0.2 /Si Multilayer

We investigate the effect of the ageing time and etching time on the etching rate of SiGe mixed etching solution, namely 1 vp HF (6%), 2 vp H₂O₂ (30%) and 3 vp CH₃COOH (99.8%). For this etching solution, we found that the etch rate of SiGe layer is saturated after the ageing time of 72 hours, and the selectivity of Si 0.8 Ge 0.2 layer and Si layer is 20:1 at ageing time of 72 hours. The collapse was appeared at the etching time of 9min with etching solution of after saturation ageing time.

Precise Analysis of Si/Graded-Si1-xGex/Si1-xGex Heterostructure Films Grown by Reduced Pressure Chemical Vapor Deposition Using Spectroscopic Ellipsometry

Precise analysis of Si/graded-Si1-xGex/ Si1-xGex heterostructure films grown by reduced pressure chemical vapor deposition using spectroscopic ellipsometry J.J. Seo, S.S. Choi, H.D. Yang, J.Y. Kim, J.W. Yang, T.H. Han*, D.H. Cho*, K.H. Shim Department of Semiconductor Science and Technology, Semiconductor Physics Research Center Chonbuk National University, 664-14 Deokjindong, Deokjinku, Jeonju, 561-756 Korea *R&D Center, Tachyonics, Seoul, Korea