| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high quality crystal growth substrate in which the densities of dislocations and cracks are low. SOLUTION: A plurality of substrate samples, each being composed of a Si substrate (ground substrate) and a GaN growth layer (substrate later), which is provided on the Si substrate, are produced on trial under the condition that the thickness of the ground substrate is defined as a variable parameter, and then after cooling the substrates to about normal temperature, each ground substrate is exfoliated and removed from each substrate layer to obtain the GaN growth layer, that is, the crystal growth substrate constituted of only the substrate layer. Thereafter, the crack density of the surface of each substrate layer is measured. For example, the crack density is lowered markedly as the Si substrate is made thinner, as shown from the results (marks) obtained by measuring each sample which has been obtained by setting the thickness of each substrate layer (GaN growth layer) to be about 7 μm. Further, the crack density markedly decreases as the substrate layer is made thicker to the same thickness of the Si substrate, as shown from the crack density of each sample of the substrate layer having a thickness of 7, 50 or 200 μm, which has been grown by using the ground substrate having the thickness of about 200 μm. |
