• Journal of electromagnetic engineering and science
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• 제5권1호
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• pp.8-13
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• 2005

The InGaP/GaAs hetero-junction bipolar transistor(HBT) monolithic voltage-controlled dielectric resonator oscillator(VCDRO) is first demonstrated for a Ku-band low noise block down-converter(LNB) system. The on-chip voltage control oscillator core employing base-collector(B-C) junction diodes is proposed for simpler frequency tuning and easy fabrication instead of the general off-chip varactor diodes. The fabricated VCDRO achieves a high output power of 6.45 to 5.31 dBm and a wide frequency tuning range of ]65 MHz( 1.53 $\%$) with a low phase noise of below -95dBc/Hz at 100 kHz offset and -115 dBc/Hz at ] MHz offset. A]so, the InGaP/GaAs HBT monolithic DRO with the same topology as the proposed VCDRO is fabricated to verify that the intrinsic low l/f noise of the HBT and the high Q of the DR contribute to the low phase noise performance. The fabricated DRO exhibits an output power of 1.33 dBm, and an extremely low phase noise of -109 dBc/Hz at 100 kHz and -131 dBc/Hz at ] MHz offset from the 10.75 GHz oscillation frequency.

• Progress in Superconductivity
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• 제7권1호
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• pp.17-21
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• 2005

We report the oscillation of the Josephson vortex-flow resistance in the rectangular stacks of $Bi_{2}Sr_{2}CaCu_{2}O_{8+x}$(Bi-2212) intrinsic Josephson junctions (IJJs). Apiece of Bi-2212 single crystal containing a few tens of IJJs was sandwiched between two gold electrodes and fabricated into a rectangular shape with the typical lateral size of about $1.5{\times}10\;{\mu}m^2$, using e-beam lithography and focused ion-beam etching techniques. In a tesla-range magnetic field applied in parallel with the junction planes, the oscillation of the Josephson vortex flow resistance was observed at temperatures near 60 K. The oscillation results from the interplay between the triangular Josephson vortex lattice and the potential barrier at the boundary of a single crystal. The oscillatory magnetoresistance for different bias currents, external magnetic fields, and the tilt-angles provides useful information on the dynamics of the coupled Josephson-vortex lattice system.

• Journal of Yeungnam Medical Science
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• 제21권1호
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• pp.67-73
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• 2004

소아에 비해 성인에서 발생한 신우요관이행 부폐색의 두드러진 임상적 특징은 소아에 비해 양측성인 경우가 현저히 적었으며, 진단이 지연되었음에도 불구하고 수술 성공률은 소아에서와 비슷하였다. 향후 소아 및 성인의 신우요관이행부폐색 환자에 대한 광범위한 임상 통계가 이루어진다면 이 질환의 정확한 자연사를 알 수 있으며, 또한 성인에서 발생한 이 질환이 태아나 소아 때부터의 질환인지, 아니면 성인이 되어 발생한 질환인지 확인할 수 있을 것이다.

• 한국세라믹학회지
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• 제29권4호
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• pp.273-282
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• 1992

The effects of intrinsic and extrinsic gettering on the formation of microdefects in the wafer and on the electrical performance at near-surfaces of three different oxygen-bearing Czochralski silicon single crystal wafers were investigated by varying the combinations of the pre-heat treatments and the phosphorus diffusion through the back-surface of the wafers. The wafers which had less than 10.9 ppma of oxygen formed no gettering zones irrespective of any pre-heat treatments, while the wafers which had more than 14.1 ppma of oxygen and were treated by Low+High pre-heat treatments generated the gettering zone comprising oxygen precipitates, staking faults, and dislocation loops. The effects of extrinsic gettering by phosphorus diffusion were evident in all samples such that the minority carrier lifetimes were increased and junction leakage currents were decreased. However, the total gettering effects among the different pre-heat treatments did not necessarily correspond to the gettering structure revealed by synchrotron radiation section topograph.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.107-108
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• 2006

ZnO is a promising material for UV or blue LEDs p-Type ZnO thin films which are imperative for the p-n junction of LEDs are difficult to achieve because of strong compensation of intrinsic defects such as zinc interstitial and oxygen vacancy. The method of codoping group three elements and group five elements is effective for the realization of p-type ZnO films. In this study, We codoped N and Al m ZnO thin films by RF magnetron sputtering and annealed the films in sputtering chamber. Some films showed p-type conductivity m Seeback effect measurement.

• Progress in Superconductivity
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• 제4권1호
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• pp.14-18
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• 2002

We had succeeded to grow bulk sing1e crystals of La／sub 2-x／Sr／sub x／$CuO_4$by the traveling solvent floating zone method (TSFZ), and to prepare La／sub 2-x／Sr／sub x／CuO$_4$single-crystalline thick films on the Zn-doped La$_2$$CuO_4$ substrate by new liquid phase epitaxial technique using an infrared heating furnace (IR-LPE). In this paper, Ireview growth of bulk single crystals and single-crystalline thick films of La／sub 2-x／Sr／sub x／$CuO_4$, and discuss on their device properties to develop high speed integrated electronic devices.

• 세라미스트
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• 제23권2호
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• pp.145-165
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• 2020

Halide perovskites are promising photovoltaic materials due to their excellent optoelectronic properties like high absorption coefficient, low exciton binding energy and long diffusion length, and single-junction solar cells consisting of them have shown a high certified efficiency of 25.2%. Despite of high efficiency, perovskite photovoltaics show poor stability under actual operational condition, which is the mostly critical obstacle for commercialization. Given that the stability of the perovskite devices is significantly affected by charge-transporting layers, the use of inorganic charge-transporting layers with better intrinsic stability than the organic counterparts must be beneficial to the enhanced device reliability. In this review article, we summarized a number of studies on the inorganic charge-transporting layers of the perovskite solar cells, especially focusing on their effects on the enhanced device reliability.

• Current Photovoltaic Research
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• 제8권1호
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• pp.6-11
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• 2020

The power conversion efficiency (PCE) of a two-terminal tandem solar cell depends upon the tunnel-recombination junction (TRJ) between the top and bottom sub-cells. An optimized TRJ in a tandem cell helps improve its open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), and efficiency (PCE). One of the parameters that affect the TRJ is the buffer layer thickness. Therefore, we investigated various TRJs by varying the thickness of the buffer or intermediate layer (TRJ-buffer) in between the highly doped p-type and n-type layers of the TRJ. The TRJ-buffer layer was p-type nc-Si:H, with a doping of 0.06%, an activation energy (E_a) of 43 meV, an optical gap (E_g) of 2.04 eV, and its thickness was varied from 0 nm to 125 nm. The tandem solar cells we investigated were a combination of a heterojunction with intrinsic thin layer (HIT) bottom sub-cell and an a-Si:H (amorphous silicon) top sub-cell. The initial cell efficiency without the TRJ buffer was 7.65% while with an optimized buffer layer, its efficiency improved to 11.74%, i.e., an improvement in efficiency by a factor of 1.53.

• 한국진공학회지
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• 제1권1호
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• pp.176-182
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• 1992

CVD 텅스텐의 응력 및 접합 누설전류 특성을 조사하였다. 응력-연속 어닐링온도 의 그래프는 냉각곡선의 응력이 가열곡선의 그것보다 더 높게 나타나는 이력현상을 보인다. SiH4 환원에 의하여 증착된 텅스텐 막이 수소환원에 의하여 증착된 막보다 전반적으로 내부 응력 뿐만 아니라 열 응력도 더 큰 것으로 나타났으며 전자가 후자에 비해 실리콘 기판과의 부착특성이 불량한 것도 이러한 응력차와 유관한 것으로 생각된다. SiH4 환원에 의하여 형 성된 텅스텐 막은 상온에서 인장 응력 상태에 있으며, 온도가 증가됨에 따라 응력이 감소하 다가 $700^{\circ}C$ 부근에서 압축 응력 상태로 바뀌고, 계속 더 온도가 증가됨에 따라 압축 응력 이 급격히 증가한다. SiH4 환원에 의한 텅스텐 막의 증착 온도가 증가함에 따라 n+/p 접합 의 누설전류가 크게 증가하며, 특히 $400^{\circ}C$로 온도가 증가함에 따라 누설전류의 증가폭이 크게 나타났는데, 이것은 수소환원 반응시와 유사하게 텅스텐의 침투(encroachment)에 의 한 실리콘 소모가 그 원인이다. SiH4/WF6 유속비의 증가에 따라서도 누설전류가 증가하는 데 그 효과는 미소한 것으로 나타났다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.446-446
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• 2011

One dimensional (1-D) structures of ZnO nanorods are promising elements for future optoelectronic devices. However there are still many obstacles in fabricating high-quality p-type ZnO up to now. In addition, it is limited to measure the degree of the doping concentration and carrier transport of the doped 1-D ZnO with conventional methods such as Hall measurement. Here we demonstrate the measurement of the electronic properties of p- and n-doped ZnO nanorods by the Kelvin probe force microscopy (KPFM). Vertically aligned ZnO nanorods with intrinsic n-doped, As-doped p-type, and p-n junction were grown by vapor phase epitaxy (VPE). Individual nanowires were then transferred onto Au films deposited on Si substrates. The morphology and surface potentials were measured simultaneously by the KPFM. The work function of the individual nanorods was estimated by comparing with that of gold film as a reference, and the doping concentration of each ZnO nanorods was deduced. Our KPFM results show that the average work function difference between the p-type and n-type regions of p-n junction ZnO nanorod is about ~85meV. This value is in good agreement with the difference in the work function between As-doped p- and n-type ZnO nanorods (96meV) measured with the same conditions. This value is smaller than the expected values estimated from the energy band diagram. However it is explained in terms of surface state and surface band bending.