How to keep type primary key when use create drop

I using spring boot and test container init db. I using postgresSql 12.1

My entity look like

@Entity
@Table(name = "student")
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student{
    @Id
    public String studentId;
    @Column
    public Int age;
    ...
}

spring.jpa.hibernate.ddl-auto=create-drop
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQL94Dialect
spring.jpa.show-sql=true

I set jpa ddl-auto create-drop but when i run test container, spring auto convert primary studentId to serial. I don't know why. I want keep studentId with type String.

Log: Create table student (student_id serial,age int)....

When i insert data looklike

INSERT INTO TABLE student (student_id,age) VALUES ("abc",1) spring throw exception because it not correct type.

Why spring auto convert primary key String to serial anh how to insert value string into field student_id. I want string don't want serial. How to fixed it.