iPhone lust is growing sharply among American teenagers, according to a note to clients issued Monday by Piper Jaffray's Gene Munster.

    Summarizing the Apple (AAPL) portion of PJC's semi-annual survey of teen buying habits, Munster reported that "Apple's dominance in the [consumer electronics] and online music markets is going seemingly unchecked."

    Specifically:

    • 31% of the U.S. teens surveyed planned to buy an iPhone in the next six months, up from 22% last fall and nearly double the 16% who wanted one a year ago.

    • 14% already own an iPhone, up from 8% a year ago, but down a point from 15% six months ago.

    • Of the 87% who own an MP3 player, 92% own an iPod. Of Apple's major competitors, only Microsoft (MSFT), Sony (SNE) and Sandisk (SNDK) showed up in the results, with 3% market share each.

    • Of the 82% of teens who download music, 43% do it legally. Of those, 92% get their music from Apple's iTunes Store.

    "We believe that the teen demographic is a critical component of long-term growth in the digital music and mobile markets," wrote Munster. "And Apple is taking its leading position in music and mobile markets."

    Piper Jaffray's 19th semi-annual teen survey questioned 6,000 students across the U.S., 261 of whom completed the Apple-related portion of the survey.