Ge p-channel tunneling FETs with steep phosphorus profile source junctions

Abstract

The solid-phase diffusion processes of three n-type dopants, i.e., phosphorus (P), arsenic (As), and antimony (Sb), from spin-on-glass (SOG) into Ge are compared. We show that P diffusion can realize both the highest impurity concentration (>7 ' 10 19 cm %3 ) and the steepest impurity profile (>10 nm/dec) among the cases of the three n-type dopants because the diffusion coefficient is strongly dependent on the dopant concentration. As a result, we can conclude that P is the most suitable dopant for the source formation of Ge p-channel TFETs. Using this P diffusion, we fabricate Ge p-channel TFETs with high-P-concentration and steep-P-profile source junctions and demonstrate their operation. A high ON current of >1.7 µA/µm is obtained at room temperature. However, the subthreshold swing and ON current/OFF current ratio are degraded by any generation-recombination-related current component. At 150 K, SS min of >108 mV/dec and ON/OFF ratio of >3.5 ' 10 5 are obtained.

Source engineering for bilayer tunnel field-effect transistor with hetero tunnel junction: thickness and impurity concentration

“…On the other hand, various combinations of III-V, SiGe and Ge semiconductor materials as components of hetero-structure tunneling junctions have also been examined. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] In particular, a hetero tunneling junction with type-II energy band alignment is promising for reducing the effective energy barrier for BTBT, leading to an exponential increase in I on .…”

(Invited) Ultrathin-Body Ge-on-Insulator MOSFET and TFET Technologies

“…We have demonstrated the operation of Ge p-TFETs with the source junctions formed by P solid phase diffusion from SOG [24]. Fig.…”

“…5 ion implantation, which can be one possible reason why there have been almost no reports on Ge p-TFETs so far. Thus, we have studied the formation of n + /p junctions by diffusion of donor impurities from Spin-on-glass (SOG) into Ge [24]. This is because we previously found that high quality p + /n junctions with steep acceptor profiles can be realized in InGaAs by Zn diffusion from SOG films [38,39].…”

“…Thus, type-II hetero-structures including Ge are expected for TFET applications. Based on these considerations, we are currently working for various TFETs using Ge, (1) Ge n-TFET [22,23] (2) Ge p-TFET [24] (3) Ge (source)/strained Si (channel) TFET [25][26][27][28] and (4) Ge (source)/oxide semiconductor (channel) TFET [29]. In this paper, we introduce the recent results of these TFETs.…”

Dopant Redistribution in High-Temperature-Grown Sb-Doped Ge Epitaxial Films

“…Because of the importance and potential application of heavily doped epitaxial n-Ge films, it has been widely studied using various approaches. Various ex situ doping techniques such as solid-phase diffusion , or ion implantation , have been demonstrated. Our attention focused on the in situ doping approach by molecular beam epitaxy (MBE), which is potentially allowing n-type Ge layers with high doping density. , The ability to produce box-shaped dopant profiles is the advantage of the in situ doping approach over the implantation or diffusion approaches. , Despite the technological advantages of in situ doping to achieve a heavily doped Ge epilayer, the underlying mechanism of the Sb dopant distribution, which is highly susceptible to the change of deposition temperatures, has not been well studied in this in situ doping approach.…”