Effect of hydrostatic pressure on the dc characteristics of AlGaN∕GaN heterojunction field effect transistors

Abstract

We report the effect of compressive hydrostatic pressure on the current-voltage characteristics of AlGaN/ GaN heterojunction field effect transistors ͑HFETs͒ on a sapphire substrate. The drain current increases with hydrostatic pressure and the maximum relative increase occurs when the gate bias is near threshold and drain bias is slightly larger than saturation bias. The increase of the drain current is associated with a pressure induced shift of the threshold voltage by −8.0 mV/ kbar that is attributed to an increase of the polarization charge density at the AlGaN/ GaN interface due to the piezoelectric effect. The results demonstrate the considerable potential of AlGaN/ GaN HFETs for strain sensor applications.

High frequency dynamic bending response of piezoresistive GaN microcantilevers

“…The theoretical estimates of GF dc for cantilevers of these dimensions are 3-15, 8,11 and higher experimental GF is attributed to the interaction of trap states. 8,[12][13][14][15] The observation of reduced GF first at low frequency (À627 to À600), and then more significantly at resonant frequency, supports the conclusion that traps play a significant role in increasing the GF over theoretical estimates. At high frequencies, it is likely that the traps and/or surface donor states, responsible for pumping charge in and out of the HFET channel (as the polarization charge changes, and the Fermi level swings up and down), 19 would not be able to respond (accept/donate charges) adequately, leading to reduction in GF, as experimentally observed.…”

“…The effect of mechanical strain, on 2DEG density and output characteristics of AlGaN/GaN heterostructure field effect transistors (HFETs), has been reported earlier. [8][9][10][11][12][13][14][15] High gauge factors (>100) have been reported for quasi-static and step bending response, 8,[12][13][14][15] however, the factors contributing to such high values, especially their deviation from much lower theoretical estimates, are poorly understood. Recently, very high gauge factor of À850 was reported for microcantilevers in transient condition, however, the corresponding dynamic response was not studied.…”

Detection of clinically relevant levels of protein analyte under physiologic buffer using planar field effect transistors

“…Despite successful use of BioFETs in some applications (Bergveld, 1991(Bergveld, , 1996Bergveld et al, 1998;Hahm and Lieber, 2004;Cui et al, 2001;Zheng et al, 2005;Star et al, 2003;Kang et al, 2005;Song and Lu, 2006;Liu et al, 2006;Neuberger et al, 2001;Kang et al, 2007); detection of proteins in physiologic buffers (with Na + concentration of 150 mM) has not been convincingly reported. One report purports to establish AlGaN/GaN BioFET protein sensing in physiologic salt (Kang et al, 2007), but presents insufficient information to substantiate this claim (see below).…”

“…AlGaN HFETs exhibit high charge sensitivity and chemically inert surfaces (Kang et al, 2005;Song and Lu, 2006;Liu et al, 2006;Neuberger et al, 2001). Charge carrier mobility in HFETs results from piezoelectric and charge displacement polarization effects arising from the AlGaN/GaN heterojunction that produces a high conductivity region known as the two-dimensional electron gas (2DEG).…”

GaN-based high-temperature and radiation-hard electronics for harsh environments

“…With these advantageous materials properties, GaN/Al x Ga 1-x N devices offer a great potential for operations in wide temperature (-230°C to 500°C) [7][8][9] and pressure (0-5kbar) ranges [10][11][12], *kson@jpl.nasa.gov and in caustic or strong radiation environments, which cannot be achieved with conventional semiconductor device technologies currently available. It has been reported that GaN/Al x Ga 1-x N heterostructure devices can reliably operate in 0-5000 bar range that the devices were tested with [10][11][12]. The goal of our current research is GaN electronics suitable for high temperature operation (500 °C) and strong radiation hardness (~ 2 Mrad).…”