Comparison of AlGaN/GaN MSM Varactor Diodes Based on HFET and MOSHFET Layer Structures

• Published in: IEEE electron device letters Vol. 27; no. 12; pp. 945 - 947
• Main Authors: Marso, M., Fox, A., Heidelberger, G., Kordos, P., Luth, H.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum gallium nitride; Aluminum gallium nitrides; Applied sciences; Capacitance; Circuit properties; Compound structure devices; Devices; Diodes; Electric, optical and optoelectronic circuits; Electrodes; Electronics; Exact sciences and technology; Fabrication; Gallium nitride; Gallium nitrides; HEMTs; Insulation; metal-insulator-semiconductor (MIS) devices; metal-oxide-semiconductor heterojunction field-effect transistors (MOSHFETs); metal-semiconductor-metal (MSM) devices; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; MODFETs; modulation-doped field-effect transistors (MODFETs); MOSHFETs; Semiconductor diodes; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Semiconductors; Transistors; Varactor diodes; Varactors; Performance evaluation; MOSFET; Gallium nitride; Cut off frequency; High electron mobility transistor; Thick film; Semiconductor metal contact; Direct current; s parameter; varactors; modulation-doped field-effect transistors (MODFETs); MMIC; Dielectric materials; Modulation doping; MSM structure; metal-semiconductor-metal (MSM) devices; Coated material; Field effect transistor; Semiconductor device; Varactor diode; Manufacturing process; Capacitance; Heterojunction field effect transistor; metal-oxide-semiconductor heterojunction field-effect transistors (MOSHFETs); Metal semiconductor field effect transistor; MIS devices; Comparative study; metal-insulator-semiconductor (MIS) devices
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2006.886705

In this letter, the performance of AlGaN/GaN-based metal-semiconductor-metal (MSM) varactor diodes based on HFET and MOSHFET layer systems is investigated. Passivated HFET MSM devices are coated with a 10-nm-thick SiO 2 layer between the electrodes; in MOSHFET-based diodes, this layer is also used as an insulator underneath the gate. Device fabrication uses standard HFET fabrication technology, allowing easy integration in monolithic microwave integrated circuits. Devices with different electrode geometry are characterized by direct current and by S-parameter measurements up to 50 GHz. The HFET-based varactors show capacitance ratios up to 14 and cutoff frequencies up to 74 GHz. The MOSHFET-based devices, on the other hand, show lower capacitance ratios and poorer stability because of the insulation layer between electrodes and semiconductor