TY - JOUR

T1 - Epitaxial Ge-Gd2O3 on Si(111) substrate by sputtering for germanium-on-insulator applications

AU - Rawat, Amita

AU - Roluahpuia, Krista Khiangte

AU - Gribisch, Philipp

AU - Osten, H. J.

AU - Laha, Apurba

AU - Mahapatra, Suddhasatta

AU - Ganguly, Udayan

N1 - Funding Information: We would like to express our heartiest regards to the Department of Science and Technology India, Ministry of Human Resource Development India, Indian instritute of Technology Nanofabrication Facility, Centre of Excellence in Nanoelectronics-IIT Bombay. P. Gribisch would like to acknowledge the Minna-James-Heineman foundation for a scholarship.

PY - 2021/8/1

Y1 - 2021/8/1

N2 - Germanium-on-insulator (GeOI) technology is a potential-alternative to the bulk-silicon based devices for radio-frequency (RF), and complementary metal oxide semiconductor applications at advanced technology nodes. A thin germanium channel is the key enabler of high mobility transistors and group-IV photonic devices. A prohibitive cost of GeOI wafers may discourage high volume manufacturing (HVM) despite promising performance. Here, we demonstrate epitaxial Gd2O3-Ge-Gd2O3 thin film growth on Si(111) substrate in an HVM platform - RF magnetron sputter system, where, the first Gd2O3 layer acts as buried-oxide (BOX) in the GeOI wafer. The second Gd2O3 layer is used as a cap-layer to be removed later using wet etching. Both the Gd2O3 layer is grown epitaxially at 750∘C, while the germanium layer is grown at room temperature and crystallised later by solid phase epitaxy (SPE) technique. The entire growth is performed without vacuum-break, to enable high throughput and excellent interface control. To compare the quality of the heterostructure, this sputter based SPE is performed on: (1) in-situ sputter grown, versus (2) ex-situ molecular-beam-epitaxy (MBE) grown epitaxial Gd2O3 BOX layer. The x-ray diffraction analysis confirms the formation of twin-free epitaxial Ge layer in the case of in-situ sputtered Gd2O3 while twinned Ge layer is observed in the case of ex-situ MBE grown Gd2O3. The twinning of the Ge layer in the ex-situ process is further supported by transmission electron microscopy analysis. Finally, we have performed an experiment to study the impact of Gd2O3 BOX layer thickness on the crystal quality of Ge layer and show that the Ge layer crystal quality remains intact irrespective of BOX layer thickness. Therefore, we have achieved twin free Ge epitaxy in RF magnetron sputter system, equivalent to in-situ All-MBE SPE process. Such a process enables low-cost GeOI wafer manufacturing for cost-effective RF transistors.

AB - Germanium-on-insulator (GeOI) technology is a potential-alternative to the bulk-silicon based devices for radio-frequency (RF), and complementary metal oxide semiconductor applications at advanced technology nodes. A thin germanium channel is the key enabler of high mobility transistors and group-IV photonic devices. A prohibitive cost of GeOI wafers may discourage high volume manufacturing (HVM) despite promising performance. Here, we demonstrate epitaxial Gd2O3-Ge-Gd2O3 thin film growth on Si(111) substrate in an HVM platform - RF magnetron sputter system, where, the first Gd2O3 layer acts as buried-oxide (BOX) in the GeOI wafer. The second Gd2O3 layer is used as a cap-layer to be removed later using wet etching. Both the Gd2O3 layer is grown epitaxially at 750∘C, while the germanium layer is grown at room temperature and crystallised later by solid phase epitaxy (SPE) technique. The entire growth is performed without vacuum-break, to enable high throughput and excellent interface control. To compare the quality of the heterostructure, this sputter based SPE is performed on: (1) in-situ sputter grown, versus (2) ex-situ molecular-beam-epitaxy (MBE) grown epitaxial Gd2O3 BOX layer. The x-ray diffraction analysis confirms the formation of twin-free epitaxial Ge layer in the case of in-situ sputtered Gd2O3 while twinned Ge layer is observed in the case of ex-situ MBE grown Gd2O3. The twinning of the Ge layer in the ex-situ process is further supported by transmission electron microscopy analysis. Finally, we have performed an experiment to study the impact of Gd2O3 BOX layer thickness on the crystal quality of Ge layer and show that the Ge layer crystal quality remains intact irrespective of BOX layer thickness. Therefore, we have achieved twin free Ge epitaxy in RF magnetron sputter system, equivalent to in-situ All-MBE SPE process. Such a process enables low-cost GeOI wafer manufacturing for cost-effective RF transistors.

KW - Epitaxial-growth

KW - Gadolinium oxide

KW - Germanium-on-insulator

KW - High volume manufacturing

KW - Radio-frequency magnetron sputter

KW - Thin film

UR - http://www.scopus.com/inward/record.url?scp=85107077278&partnerID=8YFLogxK

U2 - 10.1016/j.tsf.2021.138732

DO - 10.1016/j.tsf.2021.138732

M3 - Article

AN - SCOPUS:85107077278

VL - 731

JO - THIN SOLID FILMS

JF - THIN SOLID FILMS

SN - 0040-6090

M1 - 138732

ER -