A hole supplier and p-contact structure for a light emitting device or a photodetector, comprising: a p-type group III nitride structure configured to be formed over an active region of the light emitting device or photodetector, the p-type group III nitride structure comprising: a p-AlGaN layer, a p-AlGaN superlattice structure, or a p-AlGaN multilayer structure serving as a hole injecting and electron blocking layer and configured to be in contact with the active region; a p-type Mg-doped AlGaN or GaN channel layer on the hole injecting and electron blocking layer; a p-type AlN barrier layer on the channel layer; and another p-type Mg-doped AlGaN or GaN channel layer on the barrier layer; and a hole supplier and p-contact layer made of Al-containing group III nitride formed on the p-type group III nitride structure and being under a biaxial in-plane tensile strain, wherein the hole supplier and p-contact layer has a thickness in the range of 0.6-10 nm, the hole supplier and p-contact layer contacts the another channel layer, the hole supplier and p-contact layer is made of Al x Ga 1- x N with 0.7≤ x ≤1, the hole supplier and p-contact layer has an Al-composition equal to or higher than those of the hole injecting and electron blocking layer, the channel layers, and the barrier layer, and a room-temperature acceptor activation ratio of the hole supplier and p-contact layer is larger than 1%. a p-type group III nitride structure configured to be formed over an active region of the light emitting device or photodetector, the p-type group III nitride structure comprising: a p-AlGaN layer, a p-AlGaN superlattice structure, or a p-AlGaN multilayer structure serving as a hole injecting and electron blocking layer and configured to be in contact with the active region; a p-type Mg-doped AlGaN or GaN channel layer on the hole injecting and electron blocking layer; a p-type AlN barrier layer on the channel layer; and another p-type Mg-doped AlGaN or GaN channel layer on the barrier layer; and a hole supplier and p-contact layer made of Al-containing group III nitride formed on the p-type group III nitride structure and being under a biaxial in-plane tensile strain, wherein the hole supplier and p-contact layer has a thickness in the range of 0.6-10 nm, the hole supplier and p-contact layer contacts the another channel layer, the hole supplier and p-contact layer is made of Al x Ga 1- x N with 0.7≤ x ≤1, the hole supplier and p-contact layer has an Al-composition equal to or higher than those of the hole injecting and electron blocking layer, the channel layers, and the barrier layer, and a room-temperature acceptor activation ratio of the hole supplier and p-contact layer is larger than 1%. a p-AlGaN layer, a p-AlGaN superlattice structure, or a p-AlGaN multilayer structure serving as a hole injecting and electron blocking layer and configured to be in contact with the active region; a p-type Mg-doped AlGaN or GaN channel layer on the hole injecting and electron blocking layer; a p-type AlN barrier layer on the channel layer; and another p-type Mg-doped AlGaN or GaN channel layer on the barrier layer; and a hole supplier and p-contact layer made of Al-containing group III nitride formed on the p-type group III nitride structure and being under a biaxial in-plane tensile strain, wherein the hole supplier and p-contact layer has a thickness in the range of 0.6-10 nm, the hole supplier and p-contact layer contacts the another channel layer, the hole supplier and p-contact layer is made of Al x Ga 1- x N with 0.7≤ x ≤1, the hole supplier and p-contact layer has an Al-composition equal to or higher than those of the hole injecting and electron blocking layer, the channel layers, and the barrier layer, and a room-temperature acceptor activation ratio of the hole supplier and p-contact layer is larger than 1%.