Atomically smooth interfaces of type-II InAs/GaSb superlattice on metamorphic GaSb buffer grown in 2D mode on GaAs substrate using MBE

A. Jasik,I. Sankowska,J. Ratajczak,A. Wawro,D. Smoczyński,K. Czuba,M. Wzorek 한국물리학회 2019 Current Applied Physics Vol.19 No.2

In the paper, the comparative analysis of type-II InAs/GaSb SLs deposited on three types of GaSb buffers: homoepitaxial, metamorphic and one grown using the interfacial misfit (IMF) array technique has been presented. The buffer layers as well as superlattices were grown under nominally identical technological conditions. HRXRD investigations proved better crystal quality of the metamorphic material than the IMF-GaSb. FWHMRC were equal to 156 arcsec and 196 arcsec, respectively. The surface roughness of about 1 ML and 4 MLs was obtained using the atomic force microscope for 4.0 μm–metamorphic GaSb and 1.5 μm-IMF-GaSb layers, respectively. The etch pits density for both buffers was similar, 1–2 × 107 cm−2. Superlattice with 500 periods deposited on the homoepitaxial buffer was used as a reference of the best crystal quality. HRTEM images revealed straight InAs/GaSb interfaces with 1 ML thicknesses in this sample. The interfaces in SL deposited on IMFGaSb buffer were undulated and smeared over 3 MLs. The use of the metamorphic buffer resulted in 1–2 ML straight InAs/GaSb interfaces. The main reason for this is the roughness of IMF-GaSb buffer with mounds on the surface. Based on the obtained results we have demonstrated the advantage of metamorphic approach over IMF growth mode in GaSb/GaAs material system. A two times thicker buffer could be the price worth paying for high quality structures, even when working in the production mode.

ZnSe/ZnTe 초격자 버퍼층을 이용한 GaSb 박막성장

김시영,장지호,이상태,이웅,이홍찬,정미나,조영래 한국물리학회 2008 새물리 Vol.56 No.3

The influence on a ZnSe/ZnTe superlattice (SLS) buffer layer for on growth of GaSb films was investigated. Reflection high-electron energy diffraction (RHEED) was used to determine the thickness of relaxed ZnSe/ZnTe SLS buffer. The GaSb films with a SLS buffer were confirmed to have improved the crystal quality in terms of surface morphology and crystallinity. The SLS buffer enhances the surface morphology of GaSb by suppressing initial three-dimensional growth by reducting the lattice mismatch, which show the feasibility of using a ZnSe/ZnTe SLS buffer for the growth of high-quality GaSb films. GaAs (001) 기판 위에 ZnSe/ZnTe 초격자 버퍼층을 이용하여 분자선 에피택시법으로 성장된 GaSb 박막의 성장에 관해 연구하였다. GaSb 성장 시 ZnSe/ZnTe 초격자 버퍼층의 영향으로 초기에 2차원 성장모드가 관찰되었다. 또한 원자간력 현미경과 X선 회절법 측정을 통하여 양호한 결정성을 갖는 GaSb박막이 성장되었음을 확인하였으며, GaSb 박막의 성장을 위한 ZnSe/ZnTe 초격자 버퍼의 역할을 고찰하였다.

GaSb layers with low defect density deposited on (001) GaAs substrate in two-dimensional growth mode using molecular beam epitaxy

Agata Jasik,Iwona Sankowska,Andrzej Wawro,Jacek Ratajczak,Dariusz Smoczyński,Krzysztof Czuba 한국물리학회 2019 Current Applied Physics Vol.19 No.4

We report on the growth of fully relaxed and smooth GaSb layers with reduced density of threading dislocations, deposited on GaAs substrate. We prove that three parameters have to be controlled in order to obtain applicable GaSb buffers with atomically smooth surface: interfacial misfit (IMF), the etch pit density (EPD) and the growth mode. The GaSb/GaAs interfacial misfit array and reduced EPD ≤1.0×107 cm−2 were easily obtained using Asflux reduction for 3 min and Sb-soaking surface for 10 s before the GaSb growth initiation. The successive growth of GaSb layer proceeded under the technological conditions described by the wide range of the following parameters: rG ∈ (1.5 ÷ 1.9) Å/s, TG ∈ (400 ÷ 520)°C, V/III ∈ (2.3 ÷ 3.5). Unfortunately, a spiral or 3D growth modes were observed for this material resulting in the surface roughness of 1.1 ÷ 3.0 nm. Two-dimensional growth mode (layer by layer) can only be achieved under the strictly defined conditions. In our case, the best quality 1-μm-thick GaSb buffer layer with atomically smooth surface was obtained for the following set of parameters: rG=1.5 Å/s, TG=530 °C, V/III=2.9. The layer was characterized by the strain relaxation over 99.6%, 90° dislocations array with the average distance of 5.56 nm, EPD ∼8.0×106 cm−2 and 2D undulated terraces on the surface with roughness of about 1 ML. No mounds were observed. We belive that only thin and smooth GaSb layer with reduced EPD may be applied as the buffer layer in complex device heterostructures. Otherwise, it may cause the device parameters deterioration.

Al이 도핑된 GaInAsSb/GaSb의 경계면에서의 밴드정렬

심규리,Shim, Kyurhee 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.6

GaSb 기판위에 Al이 도핑된 GaInAsSb(Al-GaInAsSb)에 대한 최고 가전대 준위(VBM)와 최저 전도대 준위(CBM) 변화를 범용적 밀접결합방법에 근거한 해석적 근사법을 이용하여 계산하였다. GaSb와 Al-GaInAsSb 의 상대적 VBM과 CBM 준위에 따라 경계면에서의 밴드정렬 타입과 가전자대 오프셋(VBO)과 전도대 오프셋(CBO)이 결정된다. 본 논문에서는 Al 도핑이 GaInAsSb의 양이온 자리에 치환된다는 가정하에 이론이 전개 되었으며, Al은 부식등으로 결정의 질을 떨어트릴 수 있는 요인이 되므로 20 %까지 제한하였다. Al 도핑 결과, 전 구간에서 제 II 형의 밴드정렬형태를 갖게 되며, 밴드갭이 증가되는 반면 VBO와 CBO 는 감소됨을 알수 있었다. CBO 에 대한 감소비율 VBO 보다 더 크므로, Al 도핑은 경계면에서의 전자 콘트롤에 더 효율적으로 작용함을 알 수 있었다. Al-GaInAsSb은 전 구간에서 $E({\Gamma})$가 E(L)이나 E(X)보다 낮은 직접 갭을 나타 내고 있지만, Sb 성분이 많아지면(70~80 % 이상) E(L)과 E(X)이 $E({\Gamma})$에 가까워져서 전자 이동도에 영향을 주어 광학적 효율이 다소 떨어질 수 있음을 알 수 있었다. The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by $E({\Gamma})$ with a considerable distance from the E(L) and E(X), however, $E({\Gamma})$ approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.

Si 기판 GaSb 기반 p-채널 HEMT 제작을 위한 오믹 접촉 및 식각 공정에 관한 연구

윤대근,윤종원,고광만,오재응,이재성,Yoon, Dae-Keun,Yun, Jong-Won,Ko, Kwang-Man,Oh, Jae-Eung,Rieh, Jae-Sung 한국전기전자학회 2009 전기전자학회논문지 Vol.13 No.4

실리콘 기판 상에 MBE (molecular beam epitaxy)로 형성된 GaSb 기반 p-channel HEMT 소자를 제작하기 위하여 오믹 접촉 형성 공정과 식각 공정을 연구하였다. 먼저 각 소자의 절연을 위한 메사 식각 공정 연구를 수행하였으며, HF기반의 습식 식각 공정과 ICP(inductively coupled plasma)를 이용한 건식 식각 공정이 모두 사용되었다. 이와 함께 소스/드레인 영역 형성을 위한 오믹 접촉 형성 공정에 관한 연구를 진행하였으며 Ge/Au/Ni/Au 금속층 및 $300^{\circ}C$ 60초 RTA공정을 통해 $0.683\;{\Omega}mm$의 접촉 저항을 얻을 수 있었다. 더불어 HEMT 소자의 게이트 형성을 위한 게이트 리세스 공정을 AZ300 현상액과 citric산 기반의 습식 식각을 이용하여 연구하였으며, citric산의 경우 소자 구조에서 캡으로 사용된 GaSb와 베리어로 사용된 AlGaSb사이에서 높은 식각 선택비를 보였다. Ohmic contact formation and etching processes for the fabrication of MBE (molecular beam epitaxy) grown GaSb-based p-channel HEMT devices on Si substrate have been studied. Firstly, mesa etching process was established for device isolation, based on both HF-based wet etching and ICP-based dry etching. Ohmic contact process for the source and drain formation was also studied based on Ge/Au/Ni/Au metal stack, which resulted in a contact resistance as low as $0.683\;{\Omega}mm$ with RTA at $320^{\circ}C$ for 60s. Finally, for gate formation of HEMT device, gate recess process was studied based on AZ300 developer and citric acid-based wet etching, in which the latter turned out to have high etching selectivity between GaSb and AlGaSb layers that were used as the cap and the barrier of the device, respectively.

Raman and Photoluminescence Properties of Type II GaSb/GaAs Quantum Dots on (001) Ge Substrate

Zon,Thanavorn Poempool,Suwit Kiravittaya,Noppadon Nuntawong,Suwat Sopitpan,Supachok Thainoi,Songphol Kanjanachuchai,Somchai Ratanathammaphan,Somsak Panyakeow 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4

We investigate structural Raman and photoluminescence properties oftype II GaSb/GaAs quantum dots (QDs) grown on (001) Ge substrateby molecular beam epitaxy. Array of self-assembled GaSb QDshaving an areal density of ~1.66 × 1010 dots/cm2 is obtained by agrowth at relatively low substrate temperature (450 °C) on a GaAssurface segmented into anti-phase domains (APDs). Most of QDsform in one APD area. However, a few QDs can be observed at theAPD boundaries. Raman spectroscopy is used to probe the strain inGaAs layer. Slight redshift of both LO and TO GaAs peaks areobserved when GaSb QDs are buried into GaAs matrix. Opticalproperties of capped QDs are characterized by photoluminescencemeasurement at low temperatures (20 K and 30 K). Emission peaks ofGaSb/GaAs QDs are found in the range of 1.0-1.3 eV at bothtemperatures. Slight redshift is observed when the laser excitationpower is increased at 20 K while blueshift of QD peak is observed at30 K. We attribute this abnormal behavior to the contribution ofoverlapped GaSb wetting layer peak in the PL emission as well as thefeature of type II band structure.

분자선 에피탁시법으로 성장한 Te 도핑된 GaSb 박막의 전기적 특성

Aung Khaing Nyi,김시영(Si Young Kim),이웅(Woong Lee),오승준(Seungjun Oh),정미나(Mina Jung),박승환(Seunghwan Park),오동철(Dong-cheol Oh),이상태(Sang Tae Lee),조영래(Young Rae Cho),장지호(Ji Ho Chang),이홍찬(Hong Chan Lee) 한국항해항만학회 2008 한국항해항만학회 학술대회논문집 Vol.2008 No.공동학술

The electrical properties of GaSb films were investigated. Electrical properties were measured by Hal1 measurements with Van der Pauw configuration and performed in the temperature range from 10 to 300K. Te doped GaSb layers (with/without ZnTe buffer) were grown by molecular beam epitaxy. The experimental results are compared to the theory, Brooks-Herring scattering theory, based on the two-layer Hal1 effect model. We considered the four major scattering mechanisms effects. The role of ZnTe buffer to the electrical properties is discussed.

Electrical transport properties of GaSb: Te films grown by Molecular Beam Epitaxy

Aung Khaing Nyi,김시영(Si Young Kim),이웅(Woong Lee),오승준(Seungiun Oh),정미나(Mina Jung),박승환(Seunghwan Park),오동철(Dong-cheol Oh),이상태(Sang Tae Lee),조영래(Young Rae Cho),장지호(Ji Ho Chang),이홍찬(Hng Chan Lee) 한국마린엔지니어링학회 2008 한국마린엔지니어링학회 학술대회 논문집 Vol.2008 No.-

The electrical properties of GaSb films were investigated. Electrical properties were measured by Hall measurements with Van der Pauw configuration and performed in the temperature range from 10 to 300k. Te doped GaSb layers (wit/without ZnTe buffer) were grown by molecular beam epitaxy. The experimental results are compared to the theory, Brooks-Herring scattering theory, based on the two-layer Hall effect model. We considered the four major scattering mechanisms effects. The role of ZnTe buffer to the electrical properties is discussed.

The Optical and Electrical Properties of AP-MOVPE GaSb Grown Using TEGa and TMSb

S. S. Miya,V. Wagener,J. R. Botha 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.2

High quality undoped metal-organic vapour phase epitaxial (MOVPE) GaSb layers have been grown on GaAs using the trimethylantimony/triethylgallium (TMSb/TEGa) precursor combination at 550°C and atmospheric pressure. The effects of the TMSb to TEGa flux ratio (i.e. V/III ratio) on the surface morphology and optical and transport properties of these layers have been investigated. The transport properties were found to be comparable to the best reported for un-doped GaSb grown using the same precursors at low reactor pressures. Two models (using either two monovalent acceptors or one divalent acceptor) were used to estimate the density of native acceptors and the ionization energy of the acceptors in GaSb. These models showed the shallow acceptor activation energy or first ionization energy to be ~30 meV (falling within the reported range of 20 - 40 meV). The ionization energy of the deeper acceptor or second ionization of the level was determined to be ~120 meV.

GaSb/InGaAs 2-dimensional hole gas grown on InP substrate for III-V CMOS applications

신상훈,박윤호,구현철,송윤흡,송진동 한국물리학회 2017 Current Applied Physics Vol.17 No.7

We grew a two-dimensional hole gas (2DHG) system using a GaSb quantum well layer sandwiched by InGaAs layers in Molecular Beam Epitaxy (MBE). The 2DHG quantum well was achieved using a spreading modulation doping method with Be-dopant. The cross-sectional STEM image clearly shows that large dislocations by lattice-mismatch are relaxed in all layers. We confirmed substantial valence and conduction band offsets in the 2DHG by simulated results. The electrical properties were also observed by Hall measurement, indicating a high hole mobility of 653 cm2/Vs and high carrier concentration of 4.3 1012/cm2 at RT.