Compound semiconductor device with delta doped layer under etching stopper layer for decreasing resistance between active layer and ohmic electrode and process of fabrication thereof
AssigneeNEC Compound Semiconductor Devices, Ltd.
InventorsHirokazu Oikawa, Hitoshi Negishi
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Abstract
A high electron mobility transitor has a channel layer overlain by an electron supply layer held in contact with a gate electrode, and source/drain electrodes form ohmic contact together with cap layers, and resistive etching stopper are inserted between the cap layers and the electron supply layers for preventing the electron supply layer from over-etching, wherein extremely thin delta-doped layers are formed between the etching stopper layers and the electron supply layer so that the resistance between the electron supply layer and the source/drain electrodes are reduced.
Claims22
A process for fabricating a compound semiconductor device, comprising:
- a) producing a multiple-layered structure having an active layer, a delta-doped layer over said active layer, a highly resistive layer over said delta-doped layer and a highly conductive layer over said delta-doped layer on a semi-insulating substrate;
- b) removing a part of said highly conductive layer so as to expose a part of said highly resistive layer to a first opening formed between remaining portions of said highly conductive layer serving as plural cap layers using a mixture of citric acid and hydrogen peroxide, wherein said removing is terminated by oxidizing the highly resistive layer in the mixture;
- c) removing said part of said highly resistive layer and a part of said delta-doped layer thereunder so as to expose a part of said active layer to a second opening formed between plural delta doped layers respectively overlain by highly resistive layers using hydrochloric acid;
- and
- d) completing a compound semiconductor device having a first electrode held in contact with said part of said active layer and second electrodes respectively held in contact with said plural cap layers.
Dependencies are inferred from the claim text.