PURPOSE:To reduce the electrons sensitive to a boundary and suppress the decrease of carrier lifetime in a semiconductor by growing a crystal without interruption with the ratio of V group element raw material and III group element raw material being made higher in the central part of an active layer. CONSTITUTION:In an active layer, the forbidden band width is smaller in the central part. This because the natural superlattice formation depends on the V/III ratio in AlGaInP or GaInP grown by MOVPE process and the forbidden band with is made smaller as the V/III ratio is increased. Therefore, there are four boundaries at which the energy is discontinuous. The MOVPE process is crystal growing process controlled by the III group element raw material, and the supplied amount of the V group element raw material has no influence on the crystal composition and irregularity of the supply of the V group element raw material has no influence on the crystal lattice. Therefore, the crystal property at the boundary 1 is scarcely different from the crystal property of the active layer as the bulk as long as the growth is not interrupted at the interface.
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