Epitaxial wafer of compound semiconductor display device

Claim 2

In an epitaxial GaP wafer green light-emitting display device, comprising (a) a single crystalline semiconductor substrate consisting of GaP, (b) an active layer of N-doped GaP having a PN junction therein, (c) a GaP epitaxial layer formed on said single crystalline semiconductor substrate, and (d) electrode means coupled to said active layer for applying a voltage across said P-N junction, the improvement comprising a light-absorbing layer disposed between the GaP epitaxial layer and the active layer, said light-absorbing layer consisting of GaAs 1-x P x having a mixed crystal ratio (x) of 0.6 or less, a first graded epitaxial layer consisting of GaAs 1-x P x and formed between said light absorbing layer and said active layer, the mixed crystal ratio (x) of said GaAs 1-x P x first graded epitaxial layer continuously increasing in a growth direction extending from said substrate to said active layer, and a second graded epitaxial layer consisting of GaAs 1-x P x and formed between said light-absorbing layer and said GaP epitaxial layer, the mixed crystal ratio (x) of said second graded GaAs 1-x P x epitaxial layer continuously decreasing in said growth direction.

Claim 3

An epitaxial GaAsP/GaP wafer yellow or orange light-emitting display device, comprising a single crystalline semiconductor substrate consisting of GaP, an active layer of nitrogen doped GaAs 1-x P x having a PN junction therein, said active layer having a mixed crystal ratio (x) in the range from 0.5 to 1, a GaP epitaxial layer formed on said single crystalline semiconductor substrate, electrode means coupled to said active layer for applying a voltage across said PN junction, a light-absorbing layer disposed between the GaP epitaxial layer and the active layer, said light-absorbing layer consisting of GaAs 1-x P x having a mixed crystal ratio (x) smaller than that of the active layer and not more than 0.5, a first graded epitaxial layer consisting of GaAs 1-x P x and formed between said light-absorbing layer and said active layer, the mixed crystal ratio (x) of said GaAs 1-x P x first graded epitaxial layer continuously increasing in a growth direction extending from said substrate to said active layer, and a second graded epitaxial layer consisting of GaAs 1-x P x and formed between said light-absorbing layer and said GaP epitaxial layer, the mixed crystal ratio (x) of said second graded GaAS 1-x P x epitaxial layer continuously decreasing in said growth direction.

Claim 4

An epitaxial GaAsP/GaP wafer yellow or orange light-emitting display device, comprising a single crystalline semiconductor substrate consisting of GaP, an active layer of nitrogen doped GaAs 1-x P x having a PN junction therein, said active layer having a mixed crystal ratio (x) in the range from 0.5 to 1, a GaP epitaxial layer formed on said single crystalline semiconductor substrate, electrode means coupled to said active layer for applying a voltage across said PN junction, a light-absorbing layer disposed between the GaP epitaxial layer and the active layer, said light-absorbing layer consisting of GaAs 1-x P x having a mixed crystal ratio (x) smaller than that of the active layer and not more than 0.5, a first graded epitaxial layer consisting of GaAs 1-x P x and formed between said light-absorbing layer and said active layer, the mixed crystal ratio (x) of said GaAs 1-x P x first graded epitaxial layer continuously increasing in a growth direction extending from said substrate to said active layer, and a second graded epitaxial layer consisting of GaAs 1-x P x and formed between said light-absorbing layer and said GaP epitaxial layer, the mixed crystal ratio (x) of said second graded GaAS 1-x P x epitaxial layer continuously decreasing in said growth direction.