Platinum (Pt) and palladium (Pd) Schottky diodes on n-type GaN grown by metalorganic chemical vapor deposition were achieved and investigated. Aluminum was used for ohmic contacts. Barrier heights were determined to be as high as ΦB=1.13 eV by the current–voltage (I–V) method and ΦB=1.27 eV by the capacitance–voltage (C–V) method for the Pt/GaN diode, and ΦB=1.11 eV, ΦB=0.96 eV, and ΦB=1.24 eV by I–V, activation energy (I–V–T), and C–V methods for the Pd/GaN diode, respectively. The ideality factors were obtained to be n∼1.10.

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We present the first direct evidence of hot electrons traversing ballistically a thin GaAs layer. The energy distribution of the hot electrons associated with the momentum in the direction of the current was measured with the use of a tunneling-hot-electron-transfer amplifier as an electron spectrometer. The width of the ballistic peak was found to be about 60 meV for hot electrons with excess energy of some 300 meV above the thermal electrons. Those values are close to the expected initial injection values. PACS numbers: 72.20.i As the dimensions of semiconductor devices get smaller, the probability that electrons can traverse them without scattering at all, i.e. , ballistically, increases. Under these conditions the transport of electrons in the solid resembles that in vacuum, but with the effective mass and group velocity of the electrons in the semiconductor.A purely ballistic transport model was first calculated by Shur and Eastman. ' In a diode structure composed of n+-n -n+ layers, with the ballistic transport occurring in the n layer, a dc current-voltage characteristic at high injection levels was shown to obey the Child-Langmuir law I -V of a vacuum-tube diode if ideal boundary conditions were assumed. However, more realistic boundary conditions (due to carrier spillover from the n+ layers into the n layer) led to a different I Vcharacteristi-c, 2 which made the ballistic effect difficult to prove. Note also that most test structures suffered from inherent difficulties. Typical examples were large series resistances due to the Ohmic contacts and transport regions which could not be made short enough for the observation of the effect. 3 Three-terminal structures have been used as electron spectrometers and have demonstrated that hot electrons traverse thin semiconductor layers,~7 but no evidence for ballistic transport has been reported. We have measured the energy distribution of hot electrons at low temperatures, after they have traversed a thin n+-GaAs layer and were collected by a heterojunction collector. As we will show, about 50% of the injected hot electrons reached the collector without any measurable loss of energy, which proves for the first time the existence of ballistic transport in semiconductors.The energy diagram of the device used for this experiment is shown schematically in Fig.

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