p-Channel MODFET's Using GaAlAs/GaAs Two-Dimensional Hole Gas

Abstract

p-channel MODFET's were fabricated in the GaAlAs/GaAs system and the properties of the hole gas system tested to ascertain its suitability for complementary logic. The Hall mobilities on a Ga.5Al.5As/GaAs modulation-doped hole gas structure were measured to be 3650 cm2 V–1 s–1and 54000 cm2 V–1 s–1 with sheet carrier concentration of 1 × 1012 cm–2 and 7.76 × 1011 cm–2 at 77 and 4.2 K, respectively. The measured transconductances of 1.5-μ m gate-length MODFET's on this structure were measured to lie in the range of 28–35 mS mm–1 at 77 K. The field mobility measured on long gate-length MODFET's was approximately 3200 cm2V–1 s–1 at 77 K. Using test structures for measuring current voltage characteristic in the hole-gas system, low field drift mobility was measured to be 3000 cm2V–1 s–1 and velocities of 5 × 106 cm·s–1 were measured at electric fields of 3–4 kV·cm–1 at 77 K. The Schottky barriers showed low leakage and a barrier height of 0.7 to 0.8 eV. Calculations indicate that transconductances of approximately 100 mS.mm–1 should be achievable in this system for similar gate lengths. © 1984 IEEE