SEMICONDUCTOR INTEGRATED CIRCUITS

Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment

Yonghe Chen1, , Xuefeng Zheng1, Jincheng Zhang1, Xiaohua Ma2 and Yue Hao1,

+ Author Affiliations

 Corresponding author: Corresponding author. Email: canalc@163.com; Corresponding author. Email:yhao@xidian.edu.cn

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Abstract: A GaN-based E/D mode direct-couple logic 6 transistors SRAM unit and a voltage level shifter were designed and fabricated. E-mode and D-mode AlGaN/GaN HEMTs were integrated in one wafer using fluorine plasma treatment and using a moderate AlGaN barrier layer heterojunction structure. The 6 transistors SRAM unit consists of two symmetrical E/D mode inverters and two E-mode switch HEMTs. The output low and high voltage of the SRAM unit are 0.95 and 0.07 V at a voltage supply of 1 V. The voltage level shifter lowers the supply voltage using four Ni-AlGaN Schottky diodes in a series at a positive supply voltage of 6 V and a negative supply voltage of -6 V. By controlling the states of inverter modules of the level shifter in turn, the level shifter offers two channel voltage outputs of -0.5 and -5 V. The flip voltage of the level shifter is 0.76 V. Both the SRAM unit and voltage shifter operate correctly, demonstrating the promising potential for GaN-based E/D mode digital and analog integrated circuits. Several considerations are proposed to avoid the influence of threshold voltage degradation of D-mode and E-mode HEMT on the operation of the circuit.

Key words: AlGaN/GaNE/D modeSRAMvoltage level shifter



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Fig. 1.  Schematic of the proposed SRAM and voltage level shifter circuit. (a) 6 transistors SRAM unit and (b) voltage level shifter.

Fig. 2.  Key process steps of E/D mode monolithic integrated circuits (a) E- and D-mode gate definition and (b) interconnections.

Fig. 3.  Transfer characteristics of E-mode HEMTs before and after RTA.

Fig. 4.  Micrographs of fabricated circuits. (a) SRAM unit, (b) voltagelevel shifter circuit, (c) on wafer measurement of SRAM unit, and (d) on wafer measurement of voltage level shifter circuit.

Fig. 5.  (a) Subthreshold transfer characteristics at semi-log scale of D- and E-mode HEMTs, and (b) static voltage transfer curve of inverter.

Fig. 6.  Transient voltage transfer curves of SRAM unit. (a) Write ℃1℃, (b) write ℃0℃, (c) read ℃0℃, and (d) read ℃1℃.

Fig. 7.  Static voltage transfer curve of voltage level shifter.

Fig. 8.  Changes of threshold voltage of D-mode and E-mode HEMTs from 0 to 10000 s. (a) On-state and (b) Off-state.

Table 1.   Compare the voltage of output 1 and output 2.

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    Received: 27 August 2015 Revised: Online: Published: 01 May 2016

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      Yonghe Chen, Xuefeng Zheng, Jincheng Zhang, Xiaohua Ma, Yue Hao. Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment[J]. Journal of Semiconductors, 2016, 37(5): 055002. doi: 10.1088/1674-4926/37/5/055002 Y H Chen, X F Zheng, J C Zhang, X H Ma, Y Hao. Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment[J]. J. Semicond., 2016, 37(5): 055002. doi: 10.1088/1674-4926/37/5/055002.Export: BibTex EndNote
      Citation:
      Yonghe Chen, Xuefeng Zheng, Jincheng Zhang, Xiaohua Ma, Yue Hao. Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment[J]. Journal of Semiconductors, 2016, 37(5): 055002. doi: 10.1088/1674-4926/37/5/055002

      Y H Chen, X F Zheng, J C Zhang, X H Ma, Y Hao. Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment[J]. J. Semicond., 2016, 37(5): 055002. doi: 10.1088/1674-4926/37/5/055002.
      Export: BibTex EndNote

      Monolithically integrated enhancement/depletion-mode AlGaN/GaN HEMTsSRAM unit and voltage level shifter using fluorine plasma treatment

      doi: 10.1088/1674-4926/37/5/055002
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      Project supported by the National Natural Science Foundation of China (No. 61334002), the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory (No. ZHD201206), and the Program for New Century Excellent Talents in University (No. NCET-12-0915).

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      • Corresponding author: Corresponding author. Email: canalc@163.com; Corresponding author. Email:yhao@xidian.edu.cn
      • Received Date: 2015-08-27
      • Published Date: 2016-01-25

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