New pseudomorphic MODFETs utilizing Ga0.47-uIn0.53+uAs/Al0.48+uIn0.52-uAs heterostructures

A new pseudomorphic modulation-doped field-effect transistor (MODFET) utilizing a Ga0.47-uIn0.53+uAS/Al0.48+uIn0.52-uAs (u = 0.07) heterojunction on InP substrate is proposed, and has been fabricated and characterized. The molecular beam epitaxially (MBE) grown heterostructure samples have sheet carrier densities in excess of 10¹²cm^-2and exhibit electron mobilities as high as 12050, 59970, and 87300 cm2/V-sec at 300, 77, and 4.3K. The samples do not exhibit light sensitivity of persistent photoconductivity effects in any significant way Pseudomorphic MODFETs fabricated from these samples exhibit DC transconductances as high as 271 mS/ram and 227 mS/mm at room temperature for 1.6 µm and 2.9 µm gate-lengths respectively. An electron saturation velocity as high as 2.9 × 10⁷cm/sec and a unity current gain cutoff frequency of 23.5 GHZ for the 1.6 µm gate length device have been deduced. These results show that Ga0.4In0.6As/Al0.55In0.45As pseudomorphic MODFETs are very promising for high-speed and high-frequency applications.