SCIENCE CHINA Physics, Mechanics & Astronomy • Letter to the Editor • April 2017 Vol. 60 No. 4: 047022 doi: 10.1007/s11433-016-0423-3 The effect of Bi composition on the electrical properties of InP 1–x Bi x GuanNan Wei 1 , Xing Dai 2 , Qi Feng 1 , WenGang Luo 1 , YiYang Li 2 , Kai Wang 3 , LiYao Zhang 3 , WenWu Pan 3 , ShuMin Wang 3 , ShenYuan Yang 1* , and KaiYou Wang 1* 1 State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; 2 State Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China; 3 State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China Received October 26, 2016; accepted December 23, 2016; published online January 13, 2017 Citation: G. N. Wei, X. Dai, Q. Feng, W. G. Luo, Y. Y. Li, K. Wang, L. Y. Zhang, W. W. Pan, S. M. Wang, S. Y. Yang, and K. Y. Wang, The effect of Bi composition on the electrical properties of InP1–xBix, Sci. China-Phys. Mech. Astron. 60, 047022 (2017), doi: 10.1007/s11433-016-0423-3 III-V Semiconductors containing a small amount of Bi, known as dilute bismides, have attracted great interest in recent years, due to the large band-gap reduction and other unique properties [1,2]. Previous studies have been pri- marily focused on the growth and optical properties of the GaAs-based bismuthides [3], while the properties of other dilute bismides are less well understood. Berding et al. [4] theoretically predicted that InPBi is expected to be an attractive candidate for narrow-gap applications. Experi- mentally, the InPBi alloy with good single crystal quality has been successfully synthesized recently and exhibits strong and broad photoluminescence at room temperature [5,6]. However, the electric transport characteristics of the InPBi alloy are poorly understood. In this work, we systematically investigate the effect of Bi incorporation on electric transport properties of the InP 1–x Bi x alloys. Due to the large size difference between Bi and the host atoms, and the high tendency of Bi to surface segregate, low-temperature (LT) growth technique was used to grow the InPBi alloys by gas-source molecular beam epitaxy (MBE). Through variable temperature Hall measurements, electron concentration n e was observed very high (10 18 cm –3 ) for the nominally undoped InP 1–x Bi x epilayers, which nonlinearly changes with increasing x. Similar high electron concentra- *Corresponding authors (ShenYuan Yang, email: syyang@semi.ac.cn; KaiYou Wang, email: kywang@semi.ac.cn) tions have also been observed in LT grown InP [7,8], and are believed to originate from the phosphorus antisites P In via auto-ionization. The isoelectronic energy level of Bi resides in the valence band of most III-V materials [9], and Bi could not act as donors or acceptors. Thus the high electron concentration should not originate directly from Bi, but from native donor defects, similar to the LT grown InP [7,8]. In this Letter, the magnetotransport measurements and frst- principles calculations were used to determine the candidate donors in InPBi. Our frst-principles calculations show that P In has deep donor levels within the gap and leads to a mono- tonic increasing in electron concentration with increasing x. On the contrary, phosphorus vacancy V P has a donor level above the conduction band minimum (CBM), and the con- centrations of P In and V P defects show different trends with the increase of x. Thus we propose that P In and V P coexist in InPBi as donors, which can well explain the experimental observations. The 400 nm thick InP 1–x Bi x (0≤x≤2.41%) epilayers were grown on (100) semi-insulating InP substrates by V90 gas- source MBE at growth temperature of around 320°C. During the growth, elemental In and Bi fuxes were controlled by ad- justing the respective effusion cell temperatures while P 2 was cracked from PH 3 at 1000°C. After the growth, Bi compo- sitions were determined by Rutherford backscattering spec- trometry with 2.275 MeV 4 He 2+ ions. More details about the growth are published elsewhere [5,6]. Standard photolithog- © Science China Press and Springer-Verlag Berlin Heidelberg 2017 phys.scichina.com link.springer.com