Effects of Selective and Nonselective Wet Gate Recess on InAlAs∕InGaAs Metamorphic Field-Effect Transistors with Double Delta Doping in InGaAs Channels

Abstract

This investigation reports on the first symmetrically double-delta-doped channel InAlAs/InGaAs/GaAs metamorphic field-effect transistor ͑MFET͒. Two types of devices are fabricated as follows. In the fabrication of the first, the gate recessing steps are carried out using nonselective etching solution ͑phosphoric acid/hydrogen peroxide mixtures͒. In the fabrication of the second, a pH 5.5 selective succinic acid:ammonia hydrogen peroxide:water wet chemical etching liquid is adopted to form the gate recess. A succinic acid-based solution is found to be a better selective etchant of an InGaAs/InAlAs system than the more commonly used phosphoric acid-based solutions, in terms of the etching selectivity and the smoothness of the etched surface. The etch-stop mechanism is inferred from Auger electron spectroscopy to involve the formation of nonvolatile aluminum oxide, in strong agreement with the X-ray photoelectron spectroscopy spectra. Nearly kink-free current-voltage characteristics are achieved. The assessment of these structures for application in power field-effect transistor devices reveals that high frequency, high transconductance devices are feasible. As far as the authors are aware, this study is the first to compare MFETs that use a nonselective wet gate recess with those that use a selective wet gate recess.The speedily widening market for wireless communication devices in the past has increased the need for GaAs-based epitaxial materials. 1-3 Field-effect transistors ͑FETs͒ are important in today's high frequency communication systems. 4 The development of high electron mobility transistors ͑HEMTs͒ in the late 1970s in the AlGaAs/GaAs materials system gave device designers the opportunity to exploit the high mobility of undoped GaAs to improve fieldeffect transistor performance. The primary motivation for the use of the AlGaAs/GaAs system is that AlGaAs is lattice-matched to GaAs over the entire compositional range. 5,6 The GaAs/InGaAs pseudomorphic high electron mobility transistor ͑PHEMT͒ has attracted interest as an alternative to the AlGaAs/GaAs HEMTs because it exhibits excellent carrier confinement and a depressed deep-level concentration in the material with the higher bandgap, which results in persistent photoconductivity at cryogenic temperatures. 7 Most importantly, InGaAs layers on GaAs substrates have been popular for use in PHEMTs because they have favorable transport over GaAs, substrates of which are relatively cost-effective. To grow pseudomorphic strained layers, the critical thickness at which the strain in a lattice mismatched layer relaxes through the generation of misfit dislocation must be known. 8,9 An improvement over the GaAs/InGaAs PHEMT is the AlGaAs/InGaAs PHEMT with a small AlAs mole fraction, 10-12 which has a larger conduction-band discontinuity than the GaAs/InGaAs PHEMT, supporting a greater carrier concentration without experiencing the effects related to a large mole fraction of AlGaAs. Although excellent performance has been achieved by growing pseudomorphic strained ch...

Mixed-anion GaAs1−ySby graded buffer heterogeneously integrated on Si by molecular beam epitaxy

“…In order to accommodate the lattice-mismatch-induced defects between the top GaAs 0.45 Sb 0.55 layer and the Si substrate, a two-step-graded GaAsSb buffer layer with different Sb compositions was incorporated. Superior device (quantum well transistors, FETs, tunnel diodes, and TFETs) 1,[19][20][21][22][23][24][25] performances were achieved when the surface rms roughness was similar to or higher than the results reported in this work. Therefore, one can achieve excellent metamorphic device performance on this virtual substrate.…”

“…These surface roughness values are rather high, although they are comparable to the reported results for metamorphic graded buffers with lattice mismatch in the range from 4 to 8%. 1,[19][20][21][22][23][24][25] In this study, the lattice mismatch of the uppermost GaAs 0.45 Sb 0.55 layer is >12% with respect to the Si substrate, and the lattice-mismatch-induced surface roughness cannot be avoided for metamorphic growth. However, the defect control within the buffer and the uppermost GaAs 0.45 Sb 0.55 layer of interest is an important design criterion for a lattice-mismatch system and can severely impact the device performance.…”

Temperature-Dependent Study of AlGaAs/InGaAs Integrated Depletion/Enhancement-Mode High Electron Mobility Transistors with Virtual Channel Layers

“…In particular, high electron mobility transistors (HEMTs) based on the AlGaAs/GaAs material system had paid attention to high-speed digital and high-frequency microwave circuits, due to the extremely high mobility of two-dimensional electron gas (2-DEG) accumulating at the heterojunction. 1,2 Thus, the carriers in the channel could improve the output current and high frequency characteristic. However, due to the presence of 2DEG at heterojunction, the depletion-mode (D-mode) operation brings about undesired harassment on devices and circuits, such as extra-power dissipation at idle operated time.…”

Hydrogen Sensing Characteristics of AlGaInP/InGaAs Complementary Co-Integrated Pseudomorphic Doping-Channel Field-Effect Transistors

“…Recently, there has been considerable interest in the potential of III-V GaAs-based field-effect transistors (FETs) in signal amplifier and advanced logic applications. 1,2 In order to promote the performance, the GaAs channel layer could be replaced with an InGaAs strain layer because the InGaAs strain channel layer has smaller electron effective mass, higher electron mobility, and higher peak electron velocity, [3][4][5] though the In mole fraction as well as the thickness of InGaAs strain layer is critically limited. 6 Another heterostructure, i.e., In 0.5 (Ga 1-x Al x ) 0.5 P/GaAs, has attracted researcher's attention for the high-speed device and circuit applications.…”