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Pancreatic islet transplantation is an effective treatment for type I diabetes mellitus. However, many problems associated with pancreatic islet engraftment remain unresolved. In this study, we developed a hydrogel microwell device for islet implantation, fabricated by crosslinking gelatin-methacryloyl (GelMA) and 2-hydroxyethyl methacrylate (HEMA) in appropriate proportions. The fabricated hydrogel microwell device could be freeze-dried and restored by immersion in the culture medium at any time, allowing long-term storage and transport of the device for ready-to-use applications. In addition, due to its non-swelling properties, the shape of the wells of the device was maintained. Thus, the device allowed pancreatic β cell lines to form spheroids and increase insulin secretion. Intraperitoneal implantation of the β cell line-seeded GelMA/HEMA hydrogel microwell device reduced blood glucose levels in diabetic mice. In addition, they were easy to handle during transplantation and were removed from the transplant site without peritoneal adhesions or infiltration by inflammatory cells. These results suggest that the GelMA/HEMA hydrogel microwell device can go from spheroid and/or organoid fabrication to transplantation in a single step.

We fabricated a vertical metal--insulator--semiconductor field-effect transistor (MISFET) with a heterostructure launcher and an undoped channel. Vertical MISFETs exhibit a high drain current density; however, their large output conductance is a disadvantage for the open-circuit voltage gain. In a previous study, a maximum voltage gain of 4.0 was found in a vertical MISFET with a heavily doped drain region and a 45-nm-wide channel mesa. The heavily doped drain region and a narrower channel width are effective in reducing the output conductance. In this study, we fabricated a device with the heavily doped drain region and a 23-nm-wide channel mesa structure. It was observed that the output conductance decreased from 120 to 57 mS/mm at a drain current density of 0.3 MA/cm2with a narrower channel mesa. The maximum open-circuit voltage gain increased from 4.0 to 5.7.

We have realized InP/InGaAs composite-channel metal-oxide-semiconductor field-effect transistors with both selectively regrown n+-InGaAs source/drain regions and Al2O3as a gate dielectric. A 100-nm-long channel was fabricated by laterally buried regrowth in a channel undercut by metalorganic vapor phase epitaxy. The carrier density of the regrown layer was 2.9×1019cm-3. A drain current Idof 1.34 mA/µm was achieved at a drain voltage Vdof 1 V and a gate voltage Vgof 3 V. A transconductance gmof 817 µS/µm at Vd= 0.65 V was also observed at the same time. The improvement in the subthreshold slope can be explained by the decrease in dielectric/semiconductor interface trap density.

We have realized InP/InGaAs composite-channel metal-oxide-semiconductor field-effect transistors with both selectively regrown n+-InGaAs source/drain regions and Al2O3 as a gate dielectric. A 100-nm-long channel was fabricated by laterally buried regrowth in a channel undercut by metalorganic vapor phase epitaxy. The carrier density of the regrown layer was 2.9x1019 cm-3. A drain current Id of 1.34 mA/um was achieved at a drain voltage Vd of 1 V and a gate voltage Vg of 3 V. A transconductance gm of 817 uS/um at Vd = 0.65 V was also observed at the same time. The improvement in the subthreshold slope can be explained by the decrease in dielectric/semiconductor interface trap density.

We have demonstrated an InP/InGaAs composite-channel metal-oxide-semiconductor field-effect transistor with a selectively regrown n+-InGaAs source/drain formed by metal organic vapor-phase epitaxy. A 150-nm-long channel was fabricated using a dummy gate and by laterally buried regrowth in the channel undercut. The gate stack was formed after regrowth by replacing the dummy gate. The carrier density of the regrown layer was 4.9×1019cm-3. The maximum drain current at a drain voltage Vd= 1 V and a gate voltage Vg= 3 V was 0.93 mA/µm and the maximum transconductance was 0.53 mS/µm at Vd= 0.65 V.

We have demonstrated an InP/InGaAs composite-channel metal-oxide-semiconductor field-effect transistor with a selectively regrown n+-InGaAs source/drain formed by metal organic vapor-phase epitaxy. A 150-nm-long channel was fabricated using a dummy gate and by laterally buried regrowth in the channel undercut. The gate stack was formed after regrowth by replacing the dummy gate. The carrier density of the regrown layer was 4.9x1019 cm-3. The maximum drain current at a drain voltage Vd = 1 V and a gate voltage Vg = 3 V was 0.93 mA/um and the maximum transconductance was 0.53 mS/um at Vd = 0.65 V.