Performance of Surface and Gate-Engineered AlGaAs∕InGaAs Pseudomorphic High-Electron Mobility Transistors

Abstract

The epilayers in pseudomorphic high-electron mobility transistor ͑pHEMT͒ structures are grown by metallorganic chemical vapor deposition on GaAs substrates. A treatment with ammonium polysulfide ͑NH 4 ͒ 2 S X to passivate the surface of AlGaAs barrier layer is performed. Then, the surface morphology of the sulfur-treated AlGaAs layers was investigated by atomic force microscopy. The chemical compositions of AlGaAs surfaces before and after S treatment are studied using X-ray photoelectron spectroscopy. Two metals ͑Au and Pt/Au͒ are used as Schottky contacts on the gate. The passivated Pt/Au gate pHEMT outperforms the other three pHEMTs investigated in this work in both dc and high-frequency characteristics. The Schottky barrier height varies from 0.734 eV for Au on the unpassivated device to 0.904 eV for Pt/Au on the passivated device. Sulfur treatment and Pt/Au metallization yield the highest turn-on voltage and reverse breakdown voltage. An outstanding feature of this Pt/Au gate high-electron mobility transistor with passivation is its high f max . Furthermore, at 300 K, the passivated Pt/Au gate pHEMT has an exceptionally high f max /f T -ratio of 3.95. Following full characterization of these transistors at dc and radio frequencies, these devices undergo high-temperature tests. Experimental data reveal remarkably favorable characteristics of the sulfur-treated pHEMT with a Pt/Au gate. Surface and gate engineering are applied to pseudomorphic AlGaAs/InGaAs/GaAs heterostructures in the device, to achieve an unprecedented combination of high dc and high-frequency characteristics.Both commercial and military interests in high-power, highfrequency microwave transistors have fueled recent research into GaAs-based high electron mobility transistors ͑HEMTs͒. 1 The vast majority of reported HEMTs exploit AlGaAs/GaAs heterojunctions in which electrons are transferred from the heavily doped AlGaAs to the narrow bandgap GaAs. [2][3][4] No donor atoms is intentionally present in the undoped GaAs layer; thus, electrons in the twodimensional electron gas ͑2DEG͒ channel do not undergo impurity scattering; they consequently have high mobility. Initial ideas concerning the accumulation of charge at a heterojunction interface and its potential usefulness for devices was addressed in the late 1960s. Furthermore, the development of metallorganic chemical vapor deposition ͑MOCVD͒ 5 and molecular beam epitaxy ͑MBE͒ 6 technologies have made the production of heterostructures, quantum wells, and superlattices. MOCVD epitaxial growth technology was described in the scientific literature in 1968 by Manasevit, 7 even though related experimental results had been previously proposed in the patent literature by other workers, 8 prior to 1967. MOCVD technology for the growth of III-V compound semiconductors developed rapidly to dominate the production of epitaxial materials for both research and production. In 1980, researchers 9 at Fujitsu first proposed an experimental AlGaAs/GaAs HEMT and suggested the term HEMT. The selective doping of ...

High-temperature stability of improved AlGaN/AlN/GaN HEMT with pre-gate metal treatment

“…Through the surface passivation and Schottky gate metals engineering, the device characteristics and thermal stability can be improved. Additionally, passivation of heterojunction bipolar transistors (HBTs) [6] and heterostructure field-effect transistors (HFETs) [7,8,9,10] has been investigated. However, the comparison of GaN-based HEMTs with surface treatments before and after gate metal deposition has not yet to be exploited.…”

“…Transistors with high-temperature characteristics and excellent thermal stability are important for high frequency and high power applications. Many research groups have reported on the high-temperature performance of the GaAs-based HEMTs [7,8,9,11]. Nevertheless, little attention has been devoted to investigating the thermal stability of GaN-based HEMTs.…”

Microwave and power characteristics of AlGaN/GaN/Si high-electron mobility transistors with HfO2and TiO2passivation

“…One solution is to passivate the surface, enabling GaN-based HEMTs to perform at high power and high frequency. An extensive amount of literature elucidates several methods of passivating compound semiconductors [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Among the various materials for passivation that have been examined, SiN X is the most commonly used passivation dielectric for AlGaN/GaN HEMTs.…”

Comparative studies of MOS-gate/oxide-passivated AlGaAs/InGaAs pHEMTs by using ozone water oxidation technique

“…Much research effort has been devoted to stimulating various compound semiconductor-based high-electronmobility transistors (HEMTs) [1][2][3][4][5][6][7] for millimeter-wave integrated circuit (MMIC) applications because of their high carrier transport and high concentration of two-dimensional electron gas (2DEG) in the narrow-gap conduction channel. However, it is known that the gate leakages are crucial to the device performance [8], including breakdown voltage, voltage gain, RF characteristics, noise figure, power amplification and high temperature reliability.…”