MBE로 성장한 Sn/GaAs(100)층의 초기성장과 Annealing효과

우용득 동국대학교 대학원 1991 大學院硏究論集-東國大學校 大學院 Vol.21 No.-

The initial growth mode of Sn overlayers on GaAs(100) surface and the surface variation due to annealing were investigated by Auger electron spectroscopy (AES), reflection high energy electron diffraction(RHEED) and scanning electron microscopy (SEM), At room temperature, Sn was grown up to 3ML with layer by layer growth mode and with Stranski-Krastanov growth mode at higher MLs. After growing up to 10ML, crystal properties are recovered by annealing at 700K. 10ML Sn/ GaAs and GaAs/Sn/GaAs have lattice constants between GaAs and β-Sn by annealing. GaAs was grown on the Sn overlayers with thickness of 10ML and good surface morphology was achieved.

Zn 확산법에 의한 p-InP의 오믹 접촉 특성 향상

우용득,홍종성 한국물리학회 2004 새물리 Vol.49 No.2

Zn diffusion in InP and ohmic contacts to p-InP have been studied by using electrochemical capacitance voltage and current-voltage characteristics. The InP layers were grown by using metalorganic chemical vapor deposition, and Zn$_3$P$_2$ thin films were deposited on the epitaxial substrates. The samples under went rapid thermal annealing. Surface hole concentrations as high as 1 $\times$ 10$^{19}$ cm$^{-3}$ could be achieved, in contrast to the typical range of 2 $\times$ 10$^{17}$ to 2 $\times$ 10$^{18}$ cm$^{-3}$, by using the same Zn diffusion conditions. After activation, the hole concentration was two orders of magnitude higher than that of the unannealed sample at a 0.3 $\mu$m depth. When the annealing time was increased, the hole concentration remained almost constant, except at very large depths, which indicates that excess Zn interstitials existing in the doped region rapidly diffuse into the undoped region and convert into substitutional Zn. For AuZn/Zn/Au(100 \AA)/p-InP samples, the contact resistance was found to be equal to 2.8 $\times$ 10$^{-6}$ $\Omega\cdot$cm$^2$. The initial Au layer in this structure improved the contact by increasing the adhesion of the Zn to the InP. This is an excellent ohmic contact and can be used for device applications such as photodiodes and avalanche photodiodes. Zn$_3$P$_2$ 확산원 박막과 rapid thermal annealing 법을 이용하여 metalorganic chemical vapor deposition법으로 성장한 InP 박막에 Zn를 확산하였다. InP에서 Zn의 확산과 p-InP의 오믹접촉 특성을 electrochemical capacitance-voltage와 current-voltage 측정을 사용하여 조사하였다. 550 $^\circ$C에서 5 min 동안 활성화 한 후 0.3$\mu$m의 깊이에서 Zn 정공의 농도는 1 $\times$ 10$^{19}$cm$^{-3}$로, 활성화하지 않은 시료의 농도 보다 100 배 정도 더 높았다. 열처리 시간의 증가로, 도핑된 영역의 과잉의 침입형 Zn가 도핑되지 않은 영역으로 급히 확산하고 치환형 Zn로 변화하였다.AuZn/Zn/Au(100 \AA)/p-InP 시료의 접촉비저항은 2.8 $\times$ 10$^{-6}$ cm$^2$ 이었다. 낮은 접촉비저항은 Au층이 중요한 역할을 하였기 때문이다. 이 값은 매우 우수한 오믹 접촉비저항이며 광다이오드와 항복광다이오드 같은 소자의 응용에 사용할 수 있다.

급속 열화학 증착법으로 성장된 Silicon-on-sapphire의 결정성 향상을 위한 수소화 효과

우용득,박찬진 한국물리학회 2004 새물리 Vol.49 No.3

Silicon epilayers were grown on (1102) sapphire substrates by using rapid thermal chemical-vapordeposition (RTCVD). Hydrogenation treatment and thermal oxidation were done to enhance thecrystal quality and to control the epilayer thickness. From Double-crystal rocking curves and transmissionelectron microcopy sjpwed the characteristics of single-crystal Si(100) and the epilayers hadgood crystallinity and reduced defects during the hydrogenation and the thermal oxidation. Defectsand impurities near the silicon surface decreased after thermal oxidation, and mist dislocations andtwin defects between the sapphire substrate and the silicon epilayer were reduced after hydrogenation.Also, to study the defects, we performed DLTS measurement: two electron traps appearedat 0.31 eV (D1) and 0.52 eV (D2) below the conduction band. In the case of hydrogenation andthermal oxidation, D1 disappeared and D2 was decreased by about 50% compared to the value seen after thermal oxidation only.

Pseudomorphic In_xGa_(1-x)As(0.53<x<0.70)/In_0.53Al_0.47As HEMT의 전자이동도

우용득,이해익 又石大學校 1994 論文集 Vol.16 No.-

Temperature dependent Hall effect measurements were performed on the modulation doped n-type pseudomorphic In_xGa_1-xAs(x=0.53, 0.60, 0.65, and 0.70)/In_0.53Al_0 .47As HEMT grown by molecular beam epitaxy. The temperature was varied from 10K to 300K, For the sample with x=0.70, the measured value of electron mobility are 17,939,63,066, and 71,785㎠/V.s at 300, 77, and 10K respectively. Electron mobility and carrier concentration are enhanced as the In mole fraction in the channel increases. We have confirmed that the improvement is due to the reduction of alloy scattering, ionized remote impurity scattering, and intersubband scattering etc., all of which result from a large conduction band offset and increased carrier confinement in the two dimensional electron gas.

Si 기판위에 분자선 에피탁시법으로 성장된 Si_1-xGe_x 에피층의 특성

우용득,이해익 又石大學校 1996 論文集 Vol.18 No.-

The Si_(1-x)Ge_x epilayers grown on Si substrate by molecular beam epitaxy(MBE) have been studied as a function of growth temperature and Ge mole fraction by using transmission electron microscopy. double crystal x-ray diffraction, and Raman spectroscopy. TEM for these samples reveals that there are a lot of dislocations at the Si_(1-x)Ge_x/Si interface. The strain of epilayer in Si_(1-x)Ge_x was increased as the composition of Ge increases. To relaxe the strain, increment of threading dislocation was confirmed by Raman and TEM results. In the Si_(0.6)Ge_(0.4)/Si, the physical properties may be obtained when the growth temperature is held at 500℃

MBE법으로 InP 기판위에 성장한 InAlAs 에피층의 특성에 대한 성장온도의 효과

우용득,김문덕 한국진공학회 2003 Applied Science and Convergence Technology Vol.12 No.4

분자선에피탁시법을 이용하여 InP(001) 기판위에 성장한 InAlAs 에피층의 특성에 대한 성장온도 (370-$430 ^{\circ}C$)의 효과를 Normalski 현미경, 원자력현미경 (AFM), 광발광 (PL), 이중결정 x-선 회절법 (DCXRD)을 사용하여 분석하였다. InAlAs 에피층의 표면형상, 구조적, 광학적 특성은 370-$400^{\circ}C$에서 성장한 시료에서는 성장온도의 증가로 향상되지만, $430 ^{\circ}C$로 성장한 시료에서는 특성이 나빠졌다. 결과적으로 $400 ^{\circ}C$로 성장한 InAlAs 에피층의 특성이 가장 우수하였다. Indium aluminum arsenide(InAlAs) was grown by molecular beam epitaxy on (001) indium phosphide (InP) substrate and the effects of growth temperature on the properties of epitaxial layers were studied. In the temperature range of 370-$400 ^{\circ}C$, we observed that the surface morphology, optical quality and structural quality of InAlAs epilayers were improved as growth temperature increased. However, the InAlAs epilavers grown at $430 ^{\circ}C$ have the bad surface morphology and show the same trends as structural and epical quality. As a result of these measurements, it is suggested that the InAlAs epilayers of very good properties can be grown at $400 ^{\circ}C$.

RHP에서의 $Zn_3P_2$ 박막 및 RTA법에 의한 Zn 확산의 특성

우용득 한국진공학회 2004 Applied Science and Convergence Technology Vol.13 No.3

Zn diffusions in InP have been studied by electrochemical capacitance voltage. The InP layer was grown by metal organic chemical vapor deposition, and $Zn_3P_2$ thin film was deposited on the epitaxial substrates. The samples annealed in a rapid thermal annealing. It is demonstrated that surface hole concentration as high as $1\times10^{19}\textrm{cm}^{-3}$ can be achieved. When the Zn diffusion was carried at $550^{\circ}C$ and 5-20 min., the diffusion depth of hole concentration moves from 1.51$\mu\textrm{m}$ to 3.23 $\mu\textrm{m}$, and the diffusion coeffcient of Zn is $5.4\times10^{-11}\textrm{cm}^2$/sec. After activation, the concentration is two orders higher than that of untreated sample at 0.30 $\mu\textrm{m}$ depth. As the annealing time is increase, the hole concentration remains almost constant, except deep depth. It means that excess Zn interstitials exist in the doped region is rapidly diffusion into the undoped region and convert into substitutional When the thickness of $SiO_2$ thin film is above 1,000$\AA$, the hole concentration becomes stable distribution. InP에서 열처리 온도와 시간 및 활성화 온도에 따른 Zn의 확산의 특성을 electrochemical capacitance-voltage 법으로 조사하였다. InP층은 metal organic chemical vapor deposition를 이용하여 성장하였으며, 화산방법으로는 $Zn_3P_2$ 확산과 박막과 rapid thermal annealing를 사용하였다. 최대의 정공 농도를 갖는 p-lnP 층은 $550^{\circ}C$에서 5분 동안 확산과 활성화를 한 시료에서 얻었고, Zn의 농도는 $1\times10^{19}\textrm{cm}^{-3}$이었다. $550^{\circ}C$에서 5-20 분 동안 확산을 수행한 결과 정공농도의 확산 깊이는 1.51 $\mu\textrm{m}$에서 3.23 $\mu\textrm{m}$로 이동하였고, Zn의 확산계수는 $5.4\times10^{-11}\textrm{cm}^2$/sec이었다. 활성화 시간의 증가로, Zn가 더 깊게 확산하지만, 정공농도는 거의 변화가 없었다. 이는 도핑된 영역의 과잉의 침입형 Zn가 도핑되지 않은 영역으로 빠르게 확산하고 치환형 Zn로 변한다는 것을 의미한다. 정공농도는 $SiO_2$ 박막의 두께가 1,000$\AA$ 이상이어야 안정적으로 분포된다.

분자선 에피탁시로 Si 기판 위에 성장한 GaAs/Ge 에피층의 특성

우용득,이해익 우석대학교 부설 기초과학연구소 1997 기초과학연구소 논문집 Vol.2 No.-

Properties of GaAs/Ge epilayers grown using two step growth method on Si substrates by molecular beam epitaxy(MBE) are investigated using scanning electron microscopy(SEM), transmission electron microscopy(TEM), double crystal X-ray diffraction(DCXD), photolumin escence(PL) spectroscopy and Raman spectroscopy. PL. Raman and DCXD results show that the GaAs epilayer grown by two step growth method has best crystallinites. Because of the high temperature growth in two step growth method has an annealing effect upon the inital prelayer and the Ge buffer layer, resulting in the suppressed dislocatin initation.

Ge 완충층의 사용과 Ge 완충층의 in situ 열처리 온도의 변화에 대한 GaAs/Ge/Si 계면에서 전위의 거동

우용득,이해익 又石大學校 1998 論文集 Vol.20 No.-

Effect of in-situ annealing after the Ge buffer layer growth on the behavior of defects at the interfaces of GaAs/Ge/Si structure grown by molecular beam epitaxy(MBE) were investigated using transmission electron microscopy (TEM) technique. Results show that the threading dislocations toward the GaAs layers were blocked more efficiently at the Ge/GaAs interface, when an in situ thermal annealing at 750℃ for 10 minutes was performed after the Ge buffer layers Growth. It was also observed that dislocation density was independent on the thickness of Ge buffer layer. Neither stacking faults nor microtwins were observed in the samples studied. probably because surface morphology of the Ge buffer layer improved due to the in situ annealing and nucleation of the defects was suppressed a result.

분자선 에피탁시 (MBE) 법으로 InP 기판 위에 성장한 InAlAs 에피층의 특성에 대한 As4 압력의 효과

우용득,김문덕 한국물리학회 2003 새물리 Vol.47 No.6

InAlAs epilayers were grown by using molecular beam epitaxy on (001) InP substrates at a growth temperature of 410 , and the effect of the As$_4$ overpressures (V/III ratio) on the properties of the epitaxial layers were studied. For the As$_4$ overpressures of 2.1 $\times$ 10$^{-5}$ - 3.5 $\times$ 10$^{-5}$ Torr, the surface roughness of the InAlAs epilayers decreased with increasing As$_4$ overpressure. We observed that the structural quality of the InAlAs epilayers was improved as the As$_4$ overpressure was increased. In the temperature-dependent photoluminescence (PL) measurements, the PL peak energies were consistent with the PL peak energies calculated by using Varshni's equation. This result shows that the grown InAlAs epilayers were ordered InAlAs epilayers. 분자선 에피탁시법으로 InP (001) 기판 위에 As$_4$ 압력을 변화시키면서 성장한 InAlAs 에피층의 물성을 Normalski 광학현미경, 원자력현미경(AFM), 광발광(PL), 이중결정 X-선 회절법(DCXRD)을 사용하여 분석하였다. As$_4$의 압력이 2.1 $\times$ 10$^{-5}$ torr에서 3.5 $\times$ 10$^{-5}$ torr의 범위에서, InAlAs 에피층의 특성은 As$_4$의 압력이 작은 시료는 표면형상이 양호하고, As$_4$의 압력이 큰 시료는 구조적 특성이 우수하였다. 온도의존성 PL 실험에서 PL 피크 에너지는 Varshni 식으로 계산된 에너지와 잘 일치하였다. 이것은 성장된 InAlAs 박막이 질서(order)된 InAlAs 에피층임을 나타낸다.