{'fraction_non_alphanumeric': 0.037162162162162164, 'fraction_numerical': 0.0222972972972973, 'mean_word_length': 5.069672131147541, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Enhancement-Mode High Electron Mobility Transistors Lattice-Matched to InP Substrates Utilizing Ti/Pt/Au Metallization

Enhancement-mode high electron mobility transistors (EHEMTs) were fabricated on In0.52Al0.48As/In0.53Ga0.47As heterostructures lattice-matched to InP substrates. Vertical scaling of device heterostructures was carried out to realize a positive threshold voltage with Ti/Pt/Au gates. Submicron EHEMTs utilizing Ti/Pt/Au were fabricated and their performances were compared with those of conventional EHEMTs with buried-Pt gates. DC I–V characteristics of both devices exhibited excellent pinch-off characteristics and very low output conductance. Output conductance measured for both devices showed that EHEMTs exhibit smaller kink effects than normal depletion-mode HEMTs (DHEMTs) due to the operating mode of EHEMTs with forward gate bias. EHEMTs with 0.18 µm Ti/Pt/Au gates exhibited a threshold voltage of 100 mV, peak transconductance of 810 mS/mm, and unity current-gain cut-off frequency ( fT) of 150 GHz, while those with buried-Pt gates exhibited a threshold voltage of 300 mV, peak transconductance of 880 mS/mm, and unity current-gain cut-off frequency ( fT) of 100 GHz. Studies on the thermal stabilities of the two types of gate metallization have been carried out. The Ti/Pt/Au gates exhibited better thermal stability than Pt/Ti/Pt/Au gates in terms of variation of threshold voltages and maximum transconductance values at elevated temperatures.