Liquid Phase Oxidation on InGaP and Its Applications

Abstract

High-electron-mobility transistors (HEMTs) and heterojunction bipolar transistors (HBTs) have attracted many attentions in high speed and power applications due to the superior transport properties. As compared to AlGaAs pseudomorphic HEMTs (PHEMTs), InGaPrelated devices have advantages, such as higher band gaps, higher valence-band discontinuity [1], negligible deep-complex (DX) centers [2], excellent etching selectivity between InGaP and GaAs, good thermal stabilities [3-5], higher Schottky barrier heights [3], and so on. Particularly, the use of an undoped InGaP insulator takes the advantages of its low DX centers and low reactivity with oxygen [6-10], which may still suffer from the high gate leakage issue. In order to inhibit the gate leakage issue, increase the power handling capabilities, and improve the breakdown voltages, a metal-oxide-semiconductor (MOS) structure has been widely investigated. However, it is still lacks a reliable native oxide film growing on InGaP, and very few papers have reported on InGaP/InGaAs MOS-PHEMTs. In addition, the MOS-PHEMT not only has the advantages of the MOS structure (e.g., lower leakage current and higher breakdown voltage) but also has the high-density, high-mobility 2DEG channel. Over the past years, a study on the liquid phase oxidation (LPO) of InGaP near room temperature has been done [11-14]. The application of surface passivation to improve the InGaP/GaAs HBTs’ performance has also been first demonstrated [13]. The InGaP/GaAs HBTs with surface passivation by LPO exhibit significant improvement in current gain at low collector current regimes due to the reduction of surface recombination current, as compared to those without surface passivation. Moreover, a larger breakdown voltage and a lower base recombination current are also obtained. In this chapter, the oxide film composition and some issues are addressed. Then a thin InGaP native oxide film prepared by the LPO as the gate dielectric for InGaP/InGaAs MOS-PHEMTs application are discussed, and the comparisons between devices with and without LPO passivation on the InGaP/GaAs HBTs are also reviewed.