Method for producing mixed crystal wafer using special temperature control for preliminary gradient and constant layer deposition suitable for fabricating light-emitting diode

A method of manufacturing a mixed crystal compound semiconductor wafer for light emitting diodes comprising the steps of:

• providing a wafer of a semiconductor material selected from the group consisting of GaAs, GaP and InP;
• epitaxially growing a layer of the same semiconductor material as that of said substrate on said substrate;
• epitaxially growing a first gradient layer having a varying mixed crystal ratio at a constant substrate temperature with said mixed crystal ratio varying to an intermediate value from the mixed crystal ratio of said first-mentioned layer;
• epitaxially growing a first constant layer having a constant mixed crystal ratio on said first gradient layer;
• epitaxially growing a second gradient layer on said first constant layer while holding the substrate temperature constant;
• epitaxially growing a second constant layer having a mixed crystal ratio on said second gradient layer;
• epitaxially growing a third gradient layer on said second constant layer at a constant substrate temperature;
• and growing a third constant layer on said third gradient layer, a PN junction being formed in said third constant layer, said first and second constant layers being grown at a varying temperature and said third constant layer being epitaxially grown at a constant substrate temperature.

A method of manufacturing a mixed crystal compound semiconductor wafers for light emitting diodes comprising the steps of:

• providing a GaP monocrystalline substrate doped with 2.times.10.sup.17 atoms/cm.sup.3 of sulfur and having a plane oriented 6.degree. from the (100) plane toward the <110>
• direction;
• cleansing and mechanically-chemically polishing said substrate;
• disposing said substrate and high purity metallic Ga in a quartz boat in a horizontal-type quartz epitaxial reaction chamber;
• purging said reaction chamber of air;
• introducing high purity hydrogen gas into said reaction chamber at a flow rate of 650 ml/l/min relative to the volume of said reaction chamber;
• heating said high purity metallic Ga to a temperature of 760.degree. C. and said substrate to a temperature 950.degree. C.;
• introducing H.sub.2 S gas diluted with nitrogen gas to a concentration of 30 ppm into said reaction chamber at a rate of 2.6 ml/l/min;
• simultaneously introducing high purity HCl gas into said reaction chamber at a rate 10.4 ml/l/min;
• introducing PH.sub.3 gas into said reaction chamber diluted with hydrogen gas to a concentration of 12% at a flow rate of 57 ml/l/min;
• maintaining said temperature of said substrate at 950.degree. C. for 10 minutes to form a GaP epitaxial layer on said substrate;
• lowering said temperature of said substrate to 930.degree. C. over a 10 minute period to form a first constant layer;
• maintaining said temperature of said substrate at 930.degree. C. for 20 minutes while introducing AsH.sub.3 gas diluted with hydrogen gas to a concentration of 12% gradually at an increasing rate from 0 ml/l/min to 10.4 ml/l/min;
• gradually lowering said temperature of said substrate during a 10 minute period from 930.degree. C. to 910.degree. C. while maintaining constant the introduction rates of said hydrogen, said H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases;
• maintaining said temperature of said substrate at 910.degree. C. for 20 minutes while maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl and PH.sub.3 gases while gradually increasing said introduction rate of AsH.sub.3 gas to 20.8 ml/l/min;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases while lowering said temperature of said substrate from 910.degree. C. to 890.degree. C. during a 10 minute period;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl and PH.sub.3 gases and said temperature at 890.degree. C. for 20 minutes while increasing said introduction rate of said AsH.sub.3 gas to 31.2 ml/l/min;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl, PH.sub.3 and A.sub.s H.sub.3 gases and said temperature of said substrate at 890.degree. C. for 40 minutes;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases and said temperature of said substrate at 890.degree. C. for 40 minutes while introducing high purity NH.sub.3 gas at a rate of 52 ml/l/min;
• placing said wafer thus formed in a vacuum-sealed chamber with ZnAs.sub.2 in a boat of high purity quartz;
• heating said substrate to a temperature of 720.degree. C. to form a PN junction;
• and dividing said wafer into diode chips.

A method of manufacturing a mixed crystal compound semiconductor wafers for light emitting diodes comprising the steps of:

• providing a GaP monocrystalline substrate doped with 2.times.10.sup.-17 atoms/cm.sup.3 of sulfur and having a plane oriented 6.degree. from the (100) plane toward the <110>
• direction;
• cleansing and mechanically-chemically polishing said substrate;
• disposing said substrate and high purity Ga in a quartz boat in a horizontal-type quartz epitaxial reaction chamber;
• purging said reaction chamber of air;
• introducing high purity hydrogen gas into said reaction chamber at a flow rate of 700 ml/l/min relative to the volume of said reaction chamber;
• heating said substrate to a temperature 955.degree. C.;
• introducing H.sub.2 S diluted with nitrogen gas to a concentration of 30 ppm into said reaction chamber at a rate of 3.4 ml/l/min, simultaneously introducing high purity HCl gas into said reaction chamber at a rate 11.4 ml/l/min, and introducing PH.sub.3 gas into said reaction chamber diluted with hydrogen gas to a concentration of 12% at a flow rate of 64 ml/l/min, while gradually lowering said temperature of said substrate to 930.degree. during a 7 minute period to form a GaP epitaxial layer on said substrate;
• maintaining said temperature of said substrate at 930.degree. C. for 14 minutes while introducing AsH.sub.3 gas diluted with hydrogen gas to a concentration of 12% gradually at an increasing rate from 0 ml/l/min to 12.2 ml/l/min;
• gradually lowering said temperature of said substrate during a 7 minute period from 930.degree. to 905.degree. C. while maintaining constant the introduction rates of said hydrogen, said H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases;
• maintaining said temperature of said substrate at 905.degree. C. for 14 minutes while maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl and PH.sub.3 gases while gradually increasing said introduction rate of AsH.sub.3 gas to 24.4 ml/l/min;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases while lowering said temperature of said substrate from 905.degree. C. to 880.degree. C. during a 7 minute period;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl and PH.sub.3 gases and said temperature at 880.degree. C. for 14 minutes while increasing said introduction rate of said AsH.sub.3 gas to 36.6 ml/l/min;
• maintaining said introduction rates of said hydrogen, H.sub.2 S, HCl, PH.sub.3 and AsH.sub.3 gases and said temperature of said substrate at 880.degree. C. for 30 minutes while introducing high purity NH.sub.3 gas at a rate of 52 ml/l/min;
• placing said wafer thus formed in a vacuum-sealed chamber with ZnAs.sub.2 in a boat of high purity quartz;
• heating said substrate to a temperature of 720.degree. C. to form a PN junction;
• and dividing said wafer into diode chips.