| 摘要 |
PURPOSE:To reduce a leakage current in a current block layer, to decrease a parasitic capacity, to perform a low threshold value and a high speed operation, and to obtain a high manufacturing yield by employing a semiconductor layer having a P-type conductivity type between an active layer and a semiinsulating substrate. CONSTITUTION:When a semi-insulating semiconductor layer 18 is formed, a p-n junction is formed between an n-type low resistance semiconductor layer 19 generated from the face A (111) of a double hetero structure and a p-type buffer layer 11 on a semi-insulating semiconductor substrate 10a. Since this junction is formed on an InP layer having a larger forbidden band with than that of the junction in a double hetero structure, the current flowing to the former junction is sufficiently smaller than that flowing to the latter junction by the same applying voltage due to the difference of built-in potentials. As a result, the injected current flows only to an active layer, a leakage current is remarkably reduced as compared with that of a conventional one, and a low threshold value of approx. 10mA is obtained with good reproducibility. The parasitic capacity is reduced by a semi-insulating semiconductor layer 18, and a modulation band of 10GHz or more is obtained. |
