Patent Application
20200220079
The present invention relates to a compound semiconductor device that is hard to be broken and deteriorated even under a severe environment where the compound semiconductor device is exposed to high energy particles.
A compound semiconductor device is used as a field effect transistor such as a MES-FET or a HEMT (for example, see PTL 1 to PTL 3). There is a case where a device is exposed to a severe environment under which high energy particles are incident thereto, pass through a passivation film, a source field plate, and an active region of the device and reach a substrate. At this time, a large amount of electron-hole pairs are generated around a trajectory through which the high-energy particles have passed, and are diffused or recombined according to the mobility of material, a recombination speed, and an applied voltage.
A high electric field is applied between an end portion on a drain electrode side of a source field plate and an AlGaN channel layer. Therefore, when a large amount of electron-hole pairs are generated in the passivation film upon incidence of high-energy particles, a conduction path is formed at that portion, resulting in breakage. Or, there has been a problem that the concentration of holes in the vicinity of the surface of a semiconductor increases in the process of diffusion and recombination of electron-hole pairs generated in the semiconductor, which causes an increase in potential or an increase in hole current, resulting in breakage or making deterioration easy. Likewise, there has been a problem that a high electric field is applied between an end portion on a drain electrode side of a gate electrode and the AlGaN channel layer, which makes breakage or deterioration easy.
Furthermore, there has been a case where in order to improve high frequency characteristics, an SiN capacitor is connected between a gate electrode and a source electrode. However, it has been impossible to remove the charges of electron-hole pairs generated in a semiconductor via the SiN capacitor because SiN is an insulator.
The present invention has been made to solve the problems as described above, and has an object to obtain a compound semiconductor device that is hard to be broken and deteriorated even under a severe environment under which the compound semiconductor device is exposed to high energy particles.
A compound semiconductor device according to the present invention includes: a substrate; a semiconductor layer provided on the substrate; a gate electrode, a source electrode and a drain electrode provided on the semiconductor layer; and a strongly correlated electron system material connected between the gate electrode and the source electrode.
In the present invention, when electron-hole pairs are generated in the device, the strongly correlated electron system material connected to the gate electrode senses potential fluctuation in the device, and conducts phase transition from an insulator to a conductor in a short time. The electron-hole pairs generated in the device pass through the strongly correlated electron system material which has been changed to a conductive material, and flow to the ground, so that the damage to the device can be reduced. Therefore, the compound semiconductor device according to the present invention is hard to be broken and deteriorated even under a severe environment where the compound semiconductor device is exposed to high-energy particles.
A compound semiconductor device according to the embodiments of the present invention will be described with reference to the drawings. The same components will be denoted by the same symbols, and the repeated description thereof may be omitted.
A first passivation film 7 covers the gate electrode 4 and the AlGaN channel layer 3. A source field plate 9 is formed on the first passivation film 7, and extends from the source electrode 5 to a space between the gate electrode 4 and the drain electrode 6. The source field plate 9 relaxes the electric field between the gate electrode 4 and the drain electrode 6, enables a high voltage operation, and further reduces a parasitic capacitance, thereby improving high frequency characteristics. In order to protect the entire device, a second passivation film 10 covers the first passivation film 7 and the source field plate 9.
When a voltage is applied between the source electrode 5 and the drain electrode 6, and a high frequency is input to the gate electrode 4 while a desired bias voltage is applied to the gate electrode 4, electrons in two-dimensional electron gas 11 move at a high speed, whereby the compound semiconductor device operates as an amplifier capable of obtaining an amplified high frequency power from the drain electrode 6.
Representative examples of the strongly correlated electron system material 12 are VO2, SrTiO3, LaVO3, SrO, etc., and many materials showing strong correlation such as copper oxide type, Fe type, Mn type, and superconducting type have been reported. The strongly correlated electron system material 12 is an MOTT insulator exhibiting insulation properties although it is filled with electrons because the electrons have excessively strong correlation and thus do not freely move therein. It is known that when the strongly correlated electron system material 12 is stimulated with a voltage, temperature, light or the like, it conducts phase transition to a conductive material. Since the strongly correlated electron system material 12 can be formed and processed by a method which is usually used in a semiconductor process such as a PLD method, it can be easily incorporated into an existing semiconductor manufacturing process.
When high-energy particles are incident to the device, the high energy particles may pass through the second passivation film 10, the source field plate 9, the first passivation film 7, the AlGaN channel layer 3, and the GaN buffer layer 2 and reach the SiC substrate 1. Incoming particles are heavy particles, protons, electrons, neutrons, muons, etc., and have energy of about 1 keV to 100 GeV. A large amount of electron-hole pairs are generated around a trajectory through which high-energy particles have passed. In a conventional structure, the semiconductor is greatly damaged by the generated electron-hole pairs and broken or deteriorated in the process of diffusion, drift, recombination and extinction of the generated electron-hole pairs in the device.
In the present embodiment, when electron-hole pairs are generated in the device, the strongly correlated electron system material 12 connected to the gate electrode 4 senses potential fluctuation in the device, and conducts phase transition from an insulator to a conductor in a short time. The electron-hole pairs generated in the device pass through the strongly correlated electron system material 12 which has been changed to a conductive material, and flow to the ground, so that the damage to the device can be reduced. Therefore, the compound semiconductor device according to the present embodiment is hard to be broken and deteriorated even under a severe environment where the compound semiconductor device is exposed to high-energy particles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-207962 | Oct 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/088513 | 12/22/2016 | WO | 00 |
