A semiconductor light emitting device comprising: a substrate; a nucleation region; and an epitaxial structure comprising: a base region formed on the nucleation region; the base region being a quaternary AlInGaN base region, wherein the base region is at least one micrometer thick, and a III-nitride light emitting layer overlying the base region and disposed between an n-type region and a p-type region, wherein: the light emitting layer is a quaternary AlInGaN; the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm; the light emitting layer and any layers between the light emitting layer and the base region are strained; and the light emitting layer and base region are configured such that: the light emitting layer has an average InN composition b; the average InN composition b is greater than 8%; and an InN composition at any point in the light emitting layer is between (b - 0.2b) and (b + 0.2b). a substrate; a nucleation region; and an epitaxial structure comprising: a base region formed on the nucleation region; the base region being a quaternary AlInGaN base region, wherein the base region is at least one micrometer thick, and a III-nitride light emitting layer overlying the base region and disposed between an n-type region and a p-type region, wherein: the light emitting layer is a quaternary AlInGaN; the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm; the light emitting layer and any layers between the light emitting layer and the base region are strained; and the light emitting layer and base region are configured such that: the light emitting layer has an average InN composition b; the average InN composition b is greater than 8%; and an InN composition at any point in the light emitting layer is between (b - 0.2b) and (b + 0.2b). a base region formed on the nucleation region; the base region being a quaternary AlInGaN base region, wherein the base region is at least one micrometer thick, and a III-nitride light emitting layer overlying the base region and disposed between an n-type region and a p-type region, wherein: the light emitting layer is a quaternary AlInGaN; the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm; the light emitting layer and any layers between the light emitting layer and the base region are strained; and the light emitting layer and base region are configured such that: the light emitting layer has an average InN composition b; the average InN composition b is greater than 8%; and an InN composition at any point in the light emitting layer is between (b - 0.2b) and (b + 0.2b). the light emitting layer is a quaternary AlInGaN; the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm; the light emitting layer and any layers between the light emitting layer and the base region are strained; and the light emitting layer and base region are configured such that: the light emitting layer has an average InN composition b; the average InN composition b is greater than 8%; and an InN composition at any point in the light emitting layer is between (b - 0.2b) and (b + 0.2b). the light emitting layer has an average InN composition b; the average InN composition b is greater than 8%; and an InN composition at any point in the light emitting layer is between (b - 0.2b) and (b + 0.2b).