Is this correct way to generate stream cipher using AES CTR mode?
The seed should be the key and the nonce or IV. Those input parameters determine the value of the key stream. Note that the nonce may be implied if the key is not reused, in that case the key may be the only seed, with the nonce having a static value (you should however make sure that you are not vulnerable to multi-target attacks if you use a static IV, see the comment of CodesInChaos below).

For most stream ciphers - such as CTR mode of encryption - the key stream is used to encrypt the plain text by XOR'ing the plain text with the key stream. Obviously if you are just interested in the key stream of N bits then you can simply encrypt a plain text consisting of N bits set to zero (as zero is the identity element for XOR). Depending on the implementation the underlying key stream may also be available directly.