PURPOSE: To miniaturize the whole of a device and to improve the frequency characteristic of the whole of the device by making a diode PD for photodetecting, an amplifier for PD, a speaker driving circuit and a speaker on the GaAs crystal of the semi- insulating characteristic crystal-growth on an Si substrate by the monolithic structure.
CONSTITUTION: On a GaAs crystal 12 grown on a P-type Si substrate 11, a photodetecting diode PD part is made. Next, the part of an amplifier 1 for PD and a speaker driving circuit 2 is made on the GaAs crystal 12. Next, at a part of the GaAs crystal 12, an etching hole 13 is formed in a funnel shape so that the interface part of the GaAs crystal 12 and the substrate 11 comes to be wider than the surface part, and at the inner wall, the diffusion layer 15 of impurities is formed. Next, opposite to the etching hole 13, a hole is formed at the rear surface side of the substrate 11, and at the interface part of the substrate 11 and the GaAs crystal 12, a thin film- shaped diaphragm 14 is made. Next, a diffusion layer 16 is formed so as to range to the GaAs crystal 12 and the substrate 11. A speaker SP part forms a capacitor between the parts of the diffusion layer 15 and the diaphragm 14 and the diaphragm 14 is vibrated corresponding to the change of the voltage impressed between both.
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FURUKAWA JUZO
HASHIMOTO AKIHIRO
KAMIJO TAKESHI
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