Abstract: A monolithic integration of enhancement mode (E-mode) and depletion mode (D-mode) field effect transistors (FETs) comprises a compound semiconductor substrate overlaid by an epitaxial structure overlaid by source and drain electrodes. The epitaxial structure includes from bottom to top sequentially a buffer layer, a channel layer, a Schottky barrier layer, a first etch stop layer, and a first cap layer. The respective first gate metal layers of the D-mode and E-mode FET are in contact with the first etch stop layer. The D-mode and E-mode gate-sinking regions are beneath the respective first gate metal layers of the D-mode and E-mode gate electrode at least within the first etch stop layer. The first gate metal layer material of the D-mode is the same as that of the E-mode, where the first gate metal layer thickness of the E-mode is greater than that of the D-mode.

Abstract: A monolithic integrated circuit device formed in a multi-layer structure comprises a low-pinch-off-voltage pHEMT and a high-pinch-off-voltage pHEMT. A Schottky layer in the multi-layer structure contains at least three stacked regions of semiconductor material, wherein each of the two adjacent stacked regions differs in material and provides a stacked region contact interface therebetween. The gate-sinking pHEMTs each includes a gate contact, a first gate metal layer, a gate-sinking region, and a gate-sinking bottom boundary. The first gate metal layers are in contact with the topmost stacked region of the Schottky layer. The gate-sinking regions are beneath the first gate metal layers. The gate-sinking bottom boundary of the high-pinch-off-voltage pHEMT, which is closer to the semiconductor substrate than the gate-sinking bottom boundary of the low-pinch-off-voltage pHEMT, locates within 10 ? above or below one of the stacked region contact interfaces of the Schottky layer.

Abstract: A monolithic integrated circuit device formed in a multi-layer structure comprises a low-pinch-off-voltage pHEMT and a high-pinch-off-voltage pHEMT. A Schottky layer in the multi-layer structure contains at least three stacked regions of semiconductor material, wherein each of the two adjacent stacked regions differs in material and provides a stacked region contact interface therebetween. The gate-sinking pHEMTs each includes a gate contact, a first gate metal layer, a gate-sinking region, and a gate-sinking bottom boundary. The first gate metal layers are in contact with the topmost stacked region of the Schottky layer. The gate-sinking regions are beneath the first gate metal layers. The gate-sinking bottom boundary of the high-pinch-off-voltage pHEMT, which is closer to the semiconductor substrate than the gate-sinking bottom boundary of the low-pinch-off-voltage pHEMT, locates within 10 ? above or below one of the stacked region contact interfaces of the Schottky layer.

Abstract: A monolithic integration of enhancement mode (E-mode) and depletion mode (D-mode) field effect transistors (FETs) comprises a compound semiconductor substrate overlaid by an epitaxial structure overlaid by source and drain electrodes. The epitaxial structure includes from bottom to top sequentially a buffer layer, a channel layer, a Schottky barrier layer, a first etch stop layer, and a first cap layer. The respective first gate metal layers of the D-mode and E-mode FET are in contact with the first etch stop layer. The D-mode and E-mode gate-sinking regions are beneath the respective first gate metal layers of the D-mode and E-mode gate electrode at least within the first etch stop layer. The first gate metal layer material of the D-mode is the same as that of the E-mode, where the first gate metal layer thickness of the E-mode is greater than that of the D-mode.

Abstract: A monolithic integration of enhancement mode (E-mode) and depletion mode (D-mode) field effect transistors (FETs) comprises a compound semiconductor substrate overlaid by an epitaxial structure overlaid by source and drain electrodes. The epitaxial structure includes from bottom to top sequentially a buffer layer, a channel layer, a Schottky barrier layer, a first etch stop layer, and a first cap layer. The respective first gate metal layers of the D-mode and E-mode FET are in contact with the first etch stop layer. The D-mode and E-mode gate-sinking regions are beneath the respective first gate metal layers of the D-mode and E-mode gate electrode at least within the first etch stop layer. The first gate metal layer material of the D-mode is the same as that of the E-mode, where the first gate metal layer thickness of the E-mode is greater than that of the D-mode.

Abstract: A monolithic integration of enhancement mode (E-mode) and depletion mode (D-mode) field effect transistors (FETs) comprises a compound semiconductor substrate overlaid by an epitaxial structure overlaid by source and drain electrodes. The epitaxial structure includes from bottom to top sequentially a buffer layer, a channel layer, a Schottky barrier layer, a first etch stop layer, and a first cap layer. The respective first gate metal layers of the D-mode and E-mode FET are in contact with the first etch stop layer. The D-mode and E-mode gate-sinking regions are beneath the respective first gate metal layers of the D-mode and E-mode gate electrode at least within the first etch stop layer. The first gate metal layer material of the D-mode is the same as that of the E-mode, where the first gate metal layer thickness of the E-mode is greater than that of the D-mode.