SEMICONDUCTOR OPTICAL MODULATOR

摘要

1523483 Controlling light NORTHERN ELECTRIC CO Ltd 14 Aug 1975 [17 Sept 1974] 33939/75 Heading G2F A light modulator of metal-insulator-semiconductor diode construction comprises a semiconductor substrate 20 on which is formed in succession low refractive index. Semi-conductor layer 21 of the same conductive type is the substrate, a light guiding semi-conductor layer 22 which is undoped or lightly doped in the same sense as layer 21 and substrate 20 and which has a different optical absorption according to whether it is in a state of accumulation, depletion or inversion, an electrically insulating layer 23 of lower refractive index than layer 22, and a metal layer 24. A metal contact layer 25 is provided on the other side of the substrate. The layer 22 has a thickness approximately equal to the maximum depletion layer width for its doping concentration. Layer 23 may be of Si 3 N 4 ; silicon oxynitride; Al 2 O 3 ; thermally or anodically grown oxides of GaAs; or phosphorus doped SiO 2 . As particularly described, layers 21 and 22 are deposited by liquid phase epitoxy, layer 21 being 5 Á of GaAlAs containing 1% phosphorus and doped with Te to 1018 cm-3,and layer 22 being 1 Á of GaAs doped with Sn to 1015 cm-3. In Fig. 4, a light modulating diode as in Fig. 2 is combined with a light emitting diode 41, the metal layer 36 and semiconductor layers 30-32 being common. In the diode 41, after etching the insulator 33 a junction 34 is formed in layer 32 by ZnAs 2 diffusion followed by deposition and etching of metal layer 35. Alternatively, Fig. 5 (not shown), the emitting diode may be in the form of a double heterostructure requiring no diffusion. Further layers of P-type GaAlAs(P) and P-type GaAs are deposited on layer 32 after etching of layer 33, followed by formation of metal contact layers.