(Color online) Schematic diagram of the metamorphic In0.7Ga0.3As/GaAs0.35Sb0.65 p-type TFET layer structure. The source (S), channel (C), and drain (D) regions are labeled in this figure and the In0.7Ga0.3As/GaAs0.35Sb0.65 heterointerface is denoted in a box.
(Color online) Schematic band diagram of the metamorphic In0.7Ga0.3As/GaAs0.35Sb0.65 p-type TFET structure. The measured valence band offset, calculated conduction band offset, and effective tunneling barrier height (Ebeff) were also labeled in this figure.
(Color online) Symmetric (004) x-ray rocking curve of the metamorphic In0.7Ga0.3As/GaAs0.35Sb0.65 p-type TFET structure. Each layer was labeled to its corresponding peak based on early performed wet chemical etching experiments.
(Color online) (a) Symmetric (004) and (b) asymmetric (115) RSMs of the p-type TFET structure with the incident x-ray beam along [ ] direction. The RSMs together with the extracted lattice parameters confirmed the pseudomorphic nature of the active layers (In0.7Ga0.3As and GaAs0.35Sb0.65) respect to the In0.7Al0.3As buffer, which indicates that low dislocation density should be expected within the active layers.
(Color online) (a) Symmetric (004) and (b) asymmetric (115) RSMs of the p-type TFET structure with the incident x-ray beam along  direction. The strain relaxation values of In0.7Ga0.3As/GaAs0.35Sb0.65 active layers and the In0.7Al0.3As buffer are almost identical along two orthogonal ⟨110⟩ directions, which indicate symmetric strain relaxation of this structure.
(Color online) 10μm × 10μm AFM micrograph of the p-type metamorphic TFET structure. The line profiles in the two orthogonal ⟨110⟩ directions are also included. The uniform distribution of the cross-hatch pattern along  and [ ] directions suggests a symmetric strain relaxation of the linearly graded buffer layer. The AFM measurement shows a smooth surface morphology of the TFET structure with a root-mean-square (rms) roughness of 2.58 nm.
(a) Cross-sectional TEM micrograph of the p-type metamorphic TFET structure. The linearly graded InxAl1-xAs buffer layer effectively accommodates the lattice mismatch between In0.7Ga0.3As/GaAs0.35Sb0.65 active layers and the InP substrate. Only one threading dislocation was observed in the In0.7Ga0.3As/GaAs0.35Sb0.65 active layers at this magnification, indicating high crystalline quality of the p-type TFET structure. (b) and (c) cross-sectional TEM micrograph of the In0.7Ga0.3As/GaAs0.35Sb0.65 heterointerface with high magnification. A sharp heterointerface with high crystalline quality was observed.
(Color online) (a) Dynamic SIMS depth profiles of As, Sb from the p-type TFET structure. As abrupt As/Sb change with a transition less than 10 nm was confirmed, indicating low level intermixing between As and Sb at the interface. (b) Si doping profile of the p-type TFET structure. An abrupt Si doping profile with the dopant abruptness less than 2 nm/decade suggests a steep junction formed at the source/channel interface.
(Color online) (a) Room-temperature I-V characteristic of the reverse-biased n+-i-p+ diode fabricated from the p-type In0.7Ga0.3As/GaAs0.35Sb0.65 TFET structure. The room-temperature I-V characteristic of the reverse-biased p+-i-n+ diode fabricated from the n-type GaAs0.35Sb0.65/In0.7Ga0.3As TFET structure with both (b) InAs-like heterointerface and (c) GaAs-like heterointerface are also used for comparison. Similar leakage current level of the p-type TFET as that of the N-type TFET with a InAs-like heterointerface indicates that the InAs-like heterointerface with high crystalline quality was formed at source/channel interface of the p-type TFET structure.
Summary of strain relaxation properties of the p-channel TEFT structure with incident x-ray beam along [ ] and  directions.
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