Characterization of AlxGa1−xAs/GaAs heterojunction bipolar transistor structures using cross-sectional scanning force microscopy

Rosenthal, P. A.; Yu, E. T.; Pierson, R.; Zampardi, P.J.

doi:10.1063/1.372116

Cited by 29 publications

(12 citation statements)

References 18 publications

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“…It is well known that AlGaAs appears higher than GaAs because of the thicker native oxide in AlGaAs. 12 Since the surface oxide of AlGaN is mostly Al-oxide, 13 dislocations would appear as bumps if the Al concentration is higher near dislocations.…”

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confidence: 99%

Surface morphology and electronic properties of dislocations in AlGaN/GaN heterostructures

Hsu

Manfra

Lang

et al. 2001

Journal of Elec Materi

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Special Issue Paper 110The AlGaN/GaN heterstrostructures with its intrinsic two-dimensional electron gas (2DEG) is a promising materials system for high speed, high power, and high temperature electronics. Recently, it has been shown that the electron mobility (µ) of the 2DEG can exceed 50,000 cm 2 /Vs at low temperatures. 1,2 Based on what is known about the 2DEG system in AlGaAs/GaAs heterostructures, growth morphology and interface roughness could have a dramatic impact on the transport properties of the 2DEG. 3 In the AlGaN/GaN system, due to the lack of suitable substrates, dislocations and their associated electronic states present additional factors that can affect surface morphology and 2DEG transport. 4 Hence, it is important to understand how surface morphology correlates with growth conditions and the 2DEG transport properties. Due to its sub-nanometer lateral and vertical resolution, scanning force microscopy (SFM) or atomic force microscopy has become an indispensable tool for surface characterization. For thin film growth, SFM images can be used to evaluate film quality, to distinguish between two-dimensional vs. three-dimensional (island) growth modes, and to discern the existence of defects such as grain boundaries and dislocations. Dislocation mediated surface Scanning force microscopy was used to examine the surfaces of AlGaN/GaN heterostructures grown by molecular beam epitaxy (MBE) on GaN templates prepared by hydride vapor phase epitaxy (HVPE). Away from dislocations, the MBE growth replicates the surface morphology of the HVPE film, with monolayer steps clearly visible in topographic images. However, the surface morphology near dislocations depends strongly on the MBE growth conditions. Under Ga rich growth the dislocations appear as hillocks, while under stoichiometric growth they appear as pits. A dependence on Al concentration is also observed. Surface contact potential variation near dislocations is consistent with excess negative charges surrounding by a depletion region, but this was observed only for the film grown under stoichiometric conditions.

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confidence: 99%

Surface morphology and electronic properties of dislocations in AlGaN/GaN heterostructures

Hsu

Manfra

Lang

et al. 2001

Journal of Elec Materi

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“…First, it is known that V AC could have an impact on the measurement results 22 . Due to the short response time of the free carriers in the surface region voltage induced accumulation and/or depletion effects induced by V AC may occur, leading to measurement errors [22][23][24] . This effect depends on the investigated material and according to literature 22 can be reduced by lowering the modulation voltage V AC .…”

Section: Operation Principlementioning

confidence: 99%

Kelvin force microscopy on a (Al 1-x Ga x ) 0.5 In 0.5 P light-emitting diode

Katzer

Mertin

Bacher

et al. 2006

Light-Emitting Diodes: Research, Manufacturing, and Applications X

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High-brightness light-emitting diodes (LED) based on AlGaInP combines the possibility to achieve high efficiency with the flexibility of tuning the emission wavelength over a large range of the visible spectrum. For optimizing the device characteristics an accurate determination of the electronic properties, like e. g. the voltage drop across the semiconductor layer sequence, is desirable. We demonstrate the potential of Kelvin Force Microscopy for quantitative investigations of the voltage drop across the heterostructure layers of an operating AlGaInP LED. The surface potential was measured for external biases between -2.0 V and +1.86 V. By subtracting the zero bias result the voltage drop could be extracted quantitatively. In the low voltage regime, most of the voltage drops in the active layer. Above +1.5 V an additional voltage drop occurs on the p-side of the device, i. e. outside the active layer sequence, which reduces the efficiency of the LED. By comparing experimental data with simulations we will discuss possible mechanisms of these findings.

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“…This resonance-enhanced detection allows using lower ac voltages, which is preferable for semiconductor samples to avoid tip-induced band bending effects [35]. One possible implementation uses a two-pass method, where in a first scan the topography is determined, and in a second scan the mechanical oscillation is switched off and instead an ac bias at the fundamental resonance is applied, while the tip retraces the same scan line [36]. A different realization uses a higher oscillation mode for the ac frequency, that is, the second oscillation mode [37,38]; this provides the advantage of measuring simultaneously the topography and the CPD signal in one scan line.…”

Section: Kelvin Probe Force Microscopymentioning

confidence: 99%